Interventions for improving coverage of childhood immunisation in low‐ and middle‐income countries

Abstract

Background

Immunisation plays a major role in reducing childhood morbidity and mortality. Getting children immunised against potentially fatal and debilitating vaccine‐preventable diseases remains a challenge despite the availability of efficacious vaccines, particularly in low‐ and middle‐income countries. With the introduction of new vaccines, this becomes increasingly difficult. There is therefore a current need to synthesise the available evidence on the strategies used to bridge this gap. This is a second update of the Cochrane Review first published in 2011 and updated in 2016, and it focuses on interventions for improving childhood immunisation coverage in low‐ and middle‐income countries.

Objectives

To evaluate the effectiveness of intervention strategies to boost demand and supply of childhood vaccines, and sustain high childhood immunisation coverage in low‐ and middle‐income countries.

Search methods

We searched CENTRAL, MEDLINE, CINAHL, and Global Index Medicus (11 July 2022). We searched Embase, LILACS, and Sociological Abstracts (2 September 2014). We searched WHO ICTRP and ClinicalTrials.gov (11 July 2022). In addition, we screened reference lists of relevant systematic reviews for potentially eligible studies, and carried out a citation search for 14 of the included studies (19 February 2020).

Selection criteria

Eligible studies were randomised controlled trials (RCTs), non‐randomised RCTs (nRCTs), controlled before‐after studies, and interrupted time series conducted in low‐ and middle‐income countries involving children that were under five years of age, caregivers, and healthcare providers.

Data collection and analysis

We independently screened the search output, reviewed full texts of potentially eligible articles, assessed the risk of bias, and extracted data in duplicate, resolving discrepancies by consensus. We conducted random‐effects meta‐analyses and used GRADE to assess the certainty of the evidence.

Main results

Forty‐one studies involving 100,747 participants are included in the review. Twenty studies were cluster‐randomised and 15 studies were individually randomised controlled trials. Six studies were quasi‐randomised. The studies were conducted in four upper‐middle‐income countries (China, Georgia, Mexico, Guatemala), 11 lower‐middle‐income countries (Côte d'Ivoire, Ghana, Honduras, India, Indonesia, Kenya, Nigeria, Nepal, Nicaragua, Pakistan, Zimbabwe), and three lower‐income countries (Afghanistan, Mali, Rwanda).

The interventions evaluated in the studies were health education (seven studies), patient reminders (13 studies), digital register (two studies), household incentives (three studies), regular immunisation outreach sessions (two studies), home visits (one study), supportive supervision (two studies), integration of immunisation services with intermittent preventive treatment of malaria (one study), payment for performance (two studies), engagement of community leaders (one study), training on interpersonal communication skills (one study), and logistic support to health facilities (one study).

We judged nine of the included studies to have low risk of bias; the risk of bias in eight studies was unclear and 24 studies had high risk of bias.

We found low‐certainty evidence that health education (risk ratio (RR) 1.36, 95% confidence interval (CI) 1.15 to 1.62; 6 studies, 4375 participants) and home‐based records (RR 1.36, 95% CI 1.06 to 1.75; 3 studies, 4019 participants) may improve coverage with DTP3/Penta 3 vaccine. Phone calls/short messages may have little or no effect on DTP3/Penta 3 vaccine uptake (RR 1.12, 95% CI 1.00 to 1.25; 6 studies, 3869 participants; low‐certainty evidence); wearable reminders probably have little or no effect on DTP3/Penta 3 uptake (RR 1.02, 95% CI 0.97 to 1.07; 2 studies, 1567 participants; moderate‐certainty evidence). Use of community leaders in combination with provider intervention probably increases the uptake of DTP3/Penta 3 vaccine (RR 1.37, 95% CI 1.11 to 1.69; 1 study, 2020 participants; moderate‐certainty evidence). We are uncertain about the effect of immunisation outreach on DTP3/Penta 3 vaccine uptake in children under two years of age (RR 1.32, 95% CI 1.11 to 1.56; 1 study, 541 participants; very low‐certainty evidence). We are also uncertain about the following interventions improving full vaccination of children under two years of age: training of health providers on interpersonal communication skills (RR 5.65, 95% CI 3.62 to 8.83; 1 study, 420 participants; very low‐certainty evidence), and home visits (RR 1.29, 95% CI 1.15 to 1.45; 1 study, 419 participants; very low‐certainty evidence). The same applies to the effect of training of health providers on interpersonal communication skills on the uptake of DTP3/Penta 3 by one year of age (very low‐certainty evidence). The integration of immunisation with other services may, however, improve full vaccination (RR 1.29, 95% CI 1.16 to 1.44; 1 study, 1700 participants; low‐certainty evidence).

Authors' conclusions

Health education, home‐based records, a combination of involvement of community leaders with health provider intervention, and integration of immunisation services may improve vaccine uptake. The certainty of the evidence for the included interventions ranged from moderate to very low. Low certainty of the evidence implies that the true effect of the interventions might be markedly different from the estimated effect. Further, more rigorous RCTs are, therefore, required to generate high‐certainty evidence to inform policy and practice.

Plain language summary

Interventions that will increase and sustain the uptake of vaccines in low‐ and middle‐income countries

What is the aim of this review?

The aim of this Cochrane Review was to evaluate the effect of different strategies to increase the number of children in low‐ and middle‐income countries who are vaccinated to prevent infection by a disease. Researchers in Cochrane collected and analysed all relevant studies to answer this question and found 41 relevant studies.

Do strategies to improve childhood vaccination work?

Millions of children in low‐ and middle‐income countries still die from diseases that could have been prevented with vaccines, partly because the number of children that are vaccinated in this setting is still low. Governments and others have tried different strategies to increase the number of children vaccinated.

What was studied in the review?

We reviewed all interventions that aimed at improving vaccine uptake by children under the age of five years. These included interventions that target the caregivers (parents/guardians), care providers, the community, the health system, or a combination of any of these.

What are the main results of the review?

The review authors found 41 relevant studies from Afghanistan, China, Côte d'Ivoire, Ethiopia, Georgia, Ghana, Guatemala, Honduras, India, Indonesia, Kenya, Mali, Mexico, Nepal, Nicaragua, Nigeria, Pakistan, Rwanda, and Zimbabwe. These studies included 100,747 participants. They compared people receiving these strategies to people who only received the usual healthcare services. The studies showed the following.

‐ Immunisation outreach alone or in combination with non‐monetary incentives or health education probably improves full vaccination uptake among children under five years of age.

‐ Health education may lead to more children receiving three doses of diphtheria‐tetanus‐pertussis containing vaccine (DTP3).

‐ The use of specially designed immunisation cards may improve the uptake of DTP3.

‐ Using phone call or text messages to remind caregivers about vaccination may have little or no effect on improving uptake of DTP3.

‐ Involvement of community leaders in combination with health provider intervention probably improves uptake of DTP3.

‐ We are uncertain if training of health providers on interpersonal communication skills improves the uptake of DTP3.

What are the limitations of the evidence?

Our confidence in the evidence for the interventions studied ranged from moderate to very low, implying that the results of further research could differ from the results of this review. The main reasons for our reduced confidence in the evidence are that in some of the studies people were not randomly placed into different intervention groups. This means that differences between the groups could be due to differences between people rather than between the interventions. For some interventions, the results were very inconsistent across the different studies and for some only one study was available, or the intervention had few people studied.

How up‐to‐date is this review?

The review authors searched for studies that were published up to July 2022.

Summary of findings

Summary of findings 1. Health education compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Health education compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: India, Pakistan, Nepal, China, Kenya Intervention: health education Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with health education
Proportion of children who received DTP3/Penta 3 by 1 year of age Follow‐up: 3 months to 12 months	Study population		RR 1.36 (1.15 to 1.62)	4375 (6 RCTs)a	⊕⊕⊝⊝ Lowb	Health educationk may improve the proportion of children who receive DTP3 by 1 year of age.
	501 per 1000	682 per 1000 (576 to 812)
Proportion of children who received all recommended vaccines by 2 years of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received the vaccine under study (BCG) Follow‐up: 7 to 12 months	Study population		RR 0.99 (0.96 to 1.01)	1557 (2 RCTs)c	⊕⊕⊕⊝ Moderated	Health education probably makes little or no difference in improving the proportion of children who receive BCG.
	940 per 1000	931 per 1000 (903 to 950)
Proportion of children who received the vaccine under study (OPV3) Follow‐up: 12 months	Study population		RR 1.08 (1.04 to 1.11)	851 (1 RCT)e	⊕⊕⊝⊝ Lowd	Health education may slightly improve the proportion of children who receive OPV3.
	910 per 1000	983 per 1000 (946 to 1000)
Proportion of children who received the vaccine under study (HBV3) Follow‐up: 12 months	Study population		RR 1.07 (1.03 to 1.10)	851 (1 RCT)e	⊕⊕⊝⊝ Lowd	Health education may slightly improve the proportion of children who receive HBV3.
	919 per 1000	984 per 1000 (947 to 1000)
Proportion of children who received the vaccine under study (measles vaccine) Follow‐up: 7 to 12 months	Study population		RR 1.25 (1.06 to 1.47)	3343 (4 RCTs)f	⊕⊕⊝⊝ Lowd	Health education may improve the proportion of children who receive measles vaccine.
	665 per 1000	831 per 1000 (705 to 978)
Proportion of children who received other vaccine under study (BCG + DTP3 + OPV) Follow‐up: 6 months	Study population		RR 1.02 (0.96 to 1.09)	393 (1 RCT)g	⊕⊕⊝⊝ Lowd	Health education may make little or no difference in improving the proportion of children that receive a combination of BCG, DTP3, and OPV vaccines.
	929 per 1000	947 per 1000 (891 to 1000)
Received at least one vaccine Follow‐up: 12 months	Study population		RR 1.58 (1.21 to 2.05)	228 (1 RCT)h	⊕⊕⊕⊝ Moderatej	Health education probably improves the proportion of children that receive at least 1 vaccine.
	582 per 1000	483 per 1000 (373 to 623)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines Follow‐up: 7 to 12 months	Study population		RR 1.24 (1.06 to 1.44)	2387 (3 RCTs)i	⊕⊕⊝⊝ Lowb	Health education may make little or no difference in improving the proportion of children under the age of 5 years fully immunised with all scheduled vaccines.
	653 per 1000	810 per 1000 (693 to 941)
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention ‐ reported narratively in 2 studies	‐	‐	‐	‐	‐	‐
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; HBV: hepatitis B vaccine; OPV: oral polio vaccine; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded studies were Andersson 2009; Hu 2017; Owais 2011; Powell‐Jackson 2018; Usman 2009; Usman 2011.
^bWe downgraded by two levels due to serious study limitations and unexplained heterogeneity.
^cIncluded studies were Hu 2017 and Powell‐Jackson 2018.
^dWe downgraded by one level for study limitations.
^eIncluded study was Hu 2017.
^fIncluded studies were Andersson 2009; Hu 2017; Maldonado 2020; Powell‐Jackson 2018.
^gIncluded study was Bolam 1998.
^hIncluded study was Pandey 2007.
ⁱIncluded studies were Hu 2017; Maldonado 2020; Powell‐Jackson 2018.
^jWe downgraded by one level as there was only one study.
^kHealth education was community‐based group discussions held with mothers in their community settings, which involved the use of visual aids in some instances, and facility‐based health education conducted in the clinic setting with individual mothers or groups of mothers.

Summary of findings 2. Monetary incentives compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Household monetary incentives compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: Mexico, Honduras, Nicaragua, Zimbabwe Intervention: household monetary incentives Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with household monetary incentives
Proportion of children who received DTP3 or Penta 3 by 1 year of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received all recommended vaccines by 2 years of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received the vaccine under study (BCG) Follow‐up: 12 months	Study population		RR 1.00 (0.99 to 1.01)	2175 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We do not know if household monetary incentives improve the proportion of children that receive BCG vaccine because the certainty of evidence is very low.
	981 per 1000	981 per 1000 (971 to 990)
Proportion of children who received the vaccine under study (measles/MMR) ‐ household monetary incentivef Follow‐up: 12 to 24 months	Study population		RR 1.06 (0.93 to 1.21)	2709 (2 RCTs)c	⊕⊝⊝⊝ Very lowb	We do not know if household monetary incentives improve the proportion of children that receive MMR vaccine because the certainty of evidence is very low.
	869 per 1000	921 per 1000 (808 to 895)
Proportion of children who received the vaccine under study (MMR) ‐ service‐level monetary incentiveg Follow‐up: 12 months	Study population		RR 1.06 (0.95 to 1.18)	615 (1 RCT)d	⊕⊝⊝⊝ Very lowb	We do not know if service‐level monetary incentives improve the proportion of children that receive MMR vaccine because the certainty of evidence is very low.
	766 per 1000	812 per 1000 (728 to 904)
Proportion of children who received the vaccine under study (MMR) ‐ household + service‐level monetary incentive Follow‐up: 12 months	Study population		RR 1.09 (0.96 to 1.14)	456 (1 RCT)d	⊕⊝⊝⊝ Very lowb	We do not know if household plus service‐level monetary incentives improve the proportion of children that receive MMR vaccine because the certainty of evidence is very low.
	766 per 1000	835 per 1000 (736 to 950)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines Follow‐up: 13 to 24 months	Study population		RR 1.05 (0.92 to 1.20)	1000 (2 RCTs)e	⊕⊝⊝⊝ Very lowb	We do not know if household monetary incentives improve the proportion of children that receive full vaccination because the certainty of evidence is very low.
	701 per 1000	736 per 1000 (645 to 841)
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; MMR: measles, mumps, rubella; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aThe included study was Barham 2005.
^bWe downgraded by two levels for very serious study limitations.
^cThe included studies were Morris 2004 and Barham 2005.
^dThe included study is Morris 2004.
^eThe included studies were Maluccio 2004 and Robertson 2013.
^fHousehold monetary incentives ‐ vouchers worth GBP 2.53 to 3.69 given to mothers conditionally. 
^gService monetary incentives ‐ logistic support to health facilities.

Summary of findings 3. Home‐based record combined with other interventions compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Home‐based record compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children aged 1 year Setting: Pakistan and Indonesia Intervention: home‐based record Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with home‐based record
Proportion of children who received DTP3 or Penta 3 ‐ HBRf only Follow‐up: 3 to 7 months	Study population		RR 1.36 (1.06 to 1.75)	4019 (3 RCTs)a	⊕⊕⊝⊝ Lowb	Home‐based record may improve the proportion of children who receive DTP3/Penta 3 by 1 year of age.
	552 per 1000	751 per 1000 (586 to 967)
Proportion of children who received DTP3 or Penta 3 ‐ HBR + health educationg Follow‐up: 3 months	Study population		RR 1.49 (1.22 to 1.82)	1502 (2 RCTs)c	⊕⊕⊝⊝ Lowb	HBR in combination with health education may increase the proportion of children who receive DTP3/Penta 3 by 1 year of age.
	470 per 1000	700 per 1000 (574 to 856)
Proportion of children who received DTP3 or Penta 3 ‐ HBR + stickerh Follow‐up: 7 months	Study population		RR 1.46 (1.02 to 2.09)	2182 (1 RCT)d	⊕⊕⊝⊝ Lowe	HBR in combination with sticker may improve the proportion of children who receive DTP3/Penta 3.
	610 per 1000	890 per 1000 (622 to 1000)
Proportion of children who received all recommended vaccines by 2 years of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received the vaccine under study	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention presented narratively in 2 studies	‐	‐	‐	‐	‐	‐
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; HBR: home‐based record; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded studies were Usman 2009; Usman 2011; Wallace 2019. We downgraded for study limitations.
^bWe downgraded by two levels for serious study limitations and for heterogeneity.
^cIncluded studies were Usman 2009; Usman 2011. We downgraded for study limitations.
^dIncluded study was Wallace 2019.
^eWe downgraded by two levels for serious study limitations and because there was only one study.
^fHBR only ‐ redesigned immunisation card, which was larger than the normal card and had the date of the next appointment on the front and back pages.
^gHBR plus health education ‐ redesigned card described above plus facility‐based health education.
^hHBR plus sticker ‐ usual immunisation card with a bright yellow sticker.

Summary of findings 4. Digital register compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Digital register compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: India and China Intervention: digital register Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with digital register
Proportion of children who received DTP3 or Penta 3 by 1 year of age Follow‐up: 2 to 12 months	Study population		RR 0.98 (0.89 to 1.09)	328 (2 RCTs)a	⊕⊕⊕⊝ Moderateb	Digital register probably makes little or no difference in improving the proportion of children who receive DPT3/Penta3 by 1 year of age.
	904 per 1000	886 per 1000 (804 to 985)
Proportion of children who received all recommended vaccines by 2 years of age Follow‐up: 12 months	Study population		RR 1.03 (0.88 to 1.20)	205 (1 RCT)c	⊕⊕⊝⊝ Lowd	Digital register may not improve the proportion of children who receive full vaccination by 2 years of age.
	346 per 1000	357 per 1000 (305 to 415)
Proportion of children who received the vaccine under study (BCG) Follow‐up: 12 months	Study population		RR 0.98 (0.92 to 1.04)	205 (1 RCT)c	⊕⊕⊝⊝ Lowd	Digital register may not improve the proportion of children who receive BCG.
	894 per 1000	876 per 1000 (823 to 930)
Proportion of children who received the vaccine under study (OPV3) Follow‐up: 12 months	Study population		RR 1.06 (0.97 to 1.17)	205 (1 RCT)c	⊕⊕⊝⊝ Lowd	Digital register may not improve the proportion of children who receive OPV3.
	904 per 1000	958 per 1000 (877 to 1000)
Proportion of children who received the vaccine under study (measles) Follow‐up: 12 months	Study population		RR 1.06 (0.97 to 1.17)	205 (1 RCT)c	⊕⊕⊝⊝ Lowd	Digital register may not improve the proportion of children who receive measles vaccine.
	904 per 1000	958 per 1000 (877 to 1000)
Proportion of children who received the vaccine under study (HBV3) Follow‐up: 12 months	Study population		RR 0.98 (0.89 to 1.07)	205 (1 RCT)c	⊕⊕⊝⊝ Lowd	Digital register may not improve the proportion of children who receive HBV3 vaccine.
	942 per 1000	923 per 1000 (839 to 1000)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; HBV: hepatitis B vaccine; OPV: oral polio vaccine; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded studies were Chen 2016; Nagar 2018.
^bWe downgraded by one level for serious study limitations.
^cIncluded study was Chen 2016.
^dWe downgraded by two levels for serious study limitations and because there was only one study.

Summary of findings 5. Phone call/SMS with/without combination with monetary incentives compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Phone call/SMS with/without combination with monetary incentives compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: Côte d'Ivoire, Georgia, Guatemala, Kenya, Nigeria, Pakistan, Zimbabwe, India Intervention: phone call/SMS Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with phone call/SMS
Proportion of children who received DTP3 or Penta 3 by 1 year of age (phone call/SMS) Follow‐up: 3 to 12 months	Study population		RR 1.12 (1.00 to 1.25)	3869 (6 RCTs)a	⊕⊕⊝⊝ Lowb	Phone call/SMS may slightly increase the proportion of children vaccinated with DTP3/Penta 3.
	700 per 1000	784 per 1000 (700 to 875)
Proportion of children who received DTP3 or Penta 3 by 1 year of age (SMS + monetary incentive) Follow‐up: 12 months	Study population		RR 1.01 (0.98 to 1.03)	766 (1 RCT)c	⊕⊕⊝⊝ Lowd	A combination of SMS and monetary incentive may make little or no difference in improving the proportion of children that receive DTP3 vaccination.
	953 per 1000	962 per 1000 (934 to 981)
Proportion of children who received all recommended vaccines by 2 years of age (phone call/SMS only) Follow‐up: 3 to 12 months	Study population		RR 1.06 (0.99 to 1.12)	10,414 (5 RCTs)e	⊕⊕⊝⊝ Lowf	Phone call/SMS may make little or no difference in improving the proportion of children that receive full vaccination.
	679 per 1000	720 per 1000 (673 to 761)
Proportion of children who received all recommended vaccines by 2 years of age (SMS + monetary incentive) Follow‐up: 12 months	Study population		RR 1.09 (1.02 to 1.16)	766 (1 RCT)c	⊕⊕⊝⊝ Lowd	A combination of SMS and monetary incentive may slightly improve the proportion of children that receive full vaccination by 2 years of age.
	822 per 1000	896 per 1000 (839 to 954)
Proportion of children who received the vaccine under study ‐ BCG (phone call/SMS only) Follow‐up: 12 months	Study population		RR 0.98 (0.82 to 1.18)	748 (1 RCT)g	⊕⊕⊝⊝ Lowd	Phone call/SMS may make no difference in improving the proportion of children that receive BCG vaccination.
	1000 per 1000	990 per 1000 (980 to 1000)
Proportion of children who received the vaccine under study ‐ BCG (SMS + monetary incentive) Follow‐up: 12 months	Study population		RR 1.00 (0.84 to 1.20)	766 (1 RCT)g	⊕⊕⊝⊝ Lowd	Phone call/SMS in combination with monetary incentive may make no difference in improving the proportion of children that receive BCG.
	1000 per 1000	1000 per 1000 (840 per 1000)
Proportion of children who received the vaccine under study ‐ OPV3 (phone call/SMS only) Follow‐up: 6 to 12 months	Study population		RR 0.99 (0.94 to 1.05)	1069 (2 RCTs)h	⊕⊕⊕⊝ Moderatei	Phone call/SMS probably has no effect in increasing the proportion of children that receive OPV3 vaccination.
	919 per 1000	910 per 1000 (864 to 965)
Proportion of children who received the vaccine under study ‐ OPV3 (phone call/SMS + monetary incentive) Follow‐up: 3 months	Study population		RR 1.01 (0.99 to 1.04)	766 (1 RCT)c	⊕⊕⊝⊝ Lowd	Phone call/SMS in combination with monetary incentive may have little or no effect in increasing the proportion of children that receive OPV3.
	969 per 1000	979 per 1000 (960 to 1000
Proportion of children who received the vaccine under study ‐ measles/MMR (phone call/SMS + monetary incentive) Follow‐up: 12 months	Study population		RR 1.07 (1.01 to 1.14)	766 (1 RCT)c	⊕⊕⊝⊝ Lowd	Phone call/SMS in combination with monetary incentive may have little or no effect in improving the proportion of children that receive measles vaccination.
	987 per 1000	1000 per 1000 (997 to 1000)
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention ‐ reported narratively for 2 studiesk	‐	‐	‐	‐	‐	‐
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; MMR: measles, mumps, rubella; OPV: oral polio vaccine; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded studies were Bangure 2015; Dissieka 2019; Domek 2016; Ekhaguere 2019; Gibson 2017; Kazi 2018.
^bWe downgraded by two levels for study limitations and inconsistency.
^cIncluded study was Gibson 2017. We downgraded for serious study limitations.
^dWe downgraded by two levels for serious study limitations and having a single study.
^eIncluded studies were Domek 2016; Domek 2019; Gibson 2017; Kawakatsu 2020; Uddin 2016.
^fWe downgraded by two levels for serious study limitations and inconsistency.
^gIncluded study was Gibson 2017.
^hIncluded studies were Domek 2016; Gibson 2017.
ⁱWe downgraded by one level for study limitations.
^jIncluded studies were Dissieka 2019; Domek 2016; Ekhaguere 2019.
^kIncluded studies wereBangure 2015; Ekhaguere 2019.

Summary of findings 6. Wearable reminders compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Wearable reminders compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: India and Pakistan Intervention: wearable reminders Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with wearable reminders
Proportion of children who received DTP3 or Penta 3 by 1 year of age Follow‐up: 2 to 12 months	Study population		RR 1.02 (0.97 to 1.07)	1567 (2 RCTs)a	⊕⊕⊕⊝ Moderateb	Wearable reminders probably have little or no effect in improving DTP3/Penta 3 uptake. The 95% confidence interval includes both benefit and harm.
	630 per 1000	642 per 1000 (611 to 674)
Proportion of children who received all recommended vaccines by 2 years of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received the vaccine under study ‐ BCG Follow‐up: 12 months	Study population		RR 0.84 (0.74 to 0.94)	1382 (1 RCT)c	⊕⊕⊝⊝ Lowd	Wearable reminders may not increase the proportion of children receiving BCG vaccine.
	517 per 1000	434 per 1000 (382 to 486)
Proportion of children who received the vaccine under study ‐ measles Follow‐up: 12 months	Study population		RR 1.04 (0.97 to 1.12)	1440 (1 RCT)c	⊕⊕⊝⊝ Lowd	Wearable reminders may make little or no difference in improving the proportion of children vaccinated with measles vaccine.
	685 per 1000	713 per 1000 (665 to 768)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention ‐ reported narratively for 1 study	‐	‐	‐	‐	‐	‐
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded studies are Nagar 2018; Siddiqi 2020.
^bWe downgraded by one level for study limitations.
^cIncluded study was Siddiqi 2020.
^dWe downgraded by two levels for study limitations and because there was a single study.

Summary of findings 7. Training of health providers compared with routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Training of health providers compared with routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under the age of 5 years Settings: Nigeria Intervention: training of health providers Comparison: routine care
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Routine care	Training of health providers
Proportion of children who received DTP3 or Penta 3 by 1 year of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received all recommended vaccines by 2 years of age Follow‐up: 5 months	Study population		RR 5.65 (3.62 to 8.83)	420 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether interpersonal communication improves the proportion of children that receive full vaccination.
	95 per 1000	538 per 1000 (345 to 841)
Proportion of children who received the vaccine under study (BCG)	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded study is Basheer 2021, a non‐randomised controlled trial.
^bWe downgraded by three levels for very serious study limitations and because this was a single study.

Summary of findings 8. Home visit compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Home visit compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: Ghana Intervention: home visit Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with home visit
Proportion of children who received DTP3 or Penta 3 by 1 year of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received all recommended vaccines by 2 years of age Follow‐up: 6 months	Study population		RR 1.29 (1.15 to 1.45)	419 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether home visits increase the proportion of children who receive full vaccination.
	667 per 1000	860 per 1000 (767 to 967)
Proportion of children who received the vaccine under study (OPV3) Follow‐up: 6 months	Study population		RR 1.22 (1.10 to 1.35)	419 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether home visits increase the proportion of children who receive OPV3.
	731 per 1000	891 per 1000 (804 to 986)
Proportion of children who received the vaccine under study (measles) Follow‐up: 6 months	Study population		RR 1.26 (1.14 to 1.39)	419 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain if home visits increase the proportion of children who receive measles vaccine.
	726 per 1000	915 per 1000 (828 to 1000)
Number of children under 5 years of age fully immunised with all scheduled vaccines ‐ not reported	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; OPV: oral polio vaccine; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded study is Brugha 1996.
^bWe downgraded by three levels for very serious study limitations and because this was a single study.

Summary of findings 9. Immunisation outreach compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Regular immunisation outreach compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: India Intervention: regular immunisation outreach Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with regular immunisation outreach
Proportion of children who received DTP3/Penta 3 by 1 year of age Follow‐up: 12 months	Study population		RR 1.32 (1.11 to 1.56)	541 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach improves the proportion of children who receive DPT3.
	605 per 1000	799 per 1000 (671 to 944)
Proportion of children who received all recommended vaccines by 25 years of age Follow‐up: 12 months	Study population		RR 1.33 (1.00 to 1.76)	309 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach improves the proportion of children who receive all vaccines.
	516 per 1000	686 per 1000 (516 to 908)
Proportion of children who received the vaccine under study (BCG) Follow‐up: 12 months	Study population		RR 1.06 (0.99 to 1.13)	647 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach increases the proportion of children who receive BCG vaccine. The 95% confidence interval includes both benefit and harm.
	896 per 1000	949 per 1000 (887 to 1000)
Proportion of children who received the vaccine under study (HBV3) Follow‐up: 12 months	Study population		RR 1.36 (1.13 to 1.64)	541 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach increases the proportion of children who receive HBV3 vaccine.
	588 per 1000	800 per 1000 (665 to 965)
Proportion of children who received the vaccine under study (OPV3) Follow‐up: 12 months	Study population		RR 1.38 (1.16 to 1.65)	541 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach increases the proportion of children who receive OPV3 vaccine.
	580 per 1000	801 per 1000 (673 to 957)
Proportion of children who received measles vaccine Follow‐up: 12 months	Study population		RR 1.26 (0.91 to 1.74)	647 (1 RCT)a	⊕⊝⊝⊝ Very lowb	We are uncertain whether regular immunisation outreach increases the proportion of children who receive measles vaccine. The 95% confidence interval includes both benefit and harm.
	299 per 1000	376 per 1000 (272 to 519)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines (outreach only) Follow‐up: 18 months	Study population		RR 3.09 (2.11 to 4.53)	1239 (1 RCT)c	⊕⊕⊕⊝ Moderated	Regular immunisation outreach probably increases the proportion of children who receive measles vaccine.
	58 per 1000	180 per 1000 (123 to 263)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines (outreach + health education) Follow‐up: 12 months	Study population		RR 1.28 (1.23 to 1.33)	49444 (1 RCT)e	⊕⊕⊕⊝ Moderatef	Regular immunisation outreach in combination with health education probably increases the proportion of children who receive full vaccination by the age of 5 years.
	250 per 1000	320 per 1000 (308 to 333)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines (outreach + non‐monetary incentive) Follow‐up: 18 months	Study population		RR 6.66 (4.78 to 9.28)	1242 (1 RCT)c	⊕⊕⊕⊝ Moderated	Regular immunisation outreach with incentives probably increases the proportion of children who receive measles vaccine.
	58 per 1000	387 per 1000 (278 to 540)
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention ‐ reported narratively in one studyc	‐	‐	‐	‐	‐	‐
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; HBV: hepatitis B vaccine; OPV: oral polio vaccine; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded study was Sengupta 2017.
^bWe downgraded by three levels for very serious risk of bias due to study limitations (the included study was a quasi‐RCT) and for serious indirectness because there was only one study.
^cIncluded study was Banerjee 2010.
^dWe downgraded by one level for serious indirectness because there was a single study.
^eIncluded study was Habib 2017.
^fWe downgraded by one level for serious risk of bias due to study limitations.

Summary of findings 10. Integration of immunisation with other health services compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Integration of immunisation with other health services compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: Ghana Intervention: integration of immunisation with other health services Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with integration of immunisation with other health services
Proportion of children who received DTP3/Penta 3 by 1 year of age Follow‐up: 12 months	Study population		RR 1.27 (1.17 to 1.38)	2192 (1 RCT)a	⊕⊕⊝⊝ Lowb	Integration of immunisation with other health services may increase the proportion of children who receive DPT3/Penta3 by 1 year of age. However, the 95% CI includes both benefits and harms.
	602 per 1000	764 per 1000 (704 to 831)
Proportion of children who received all recommended vaccines by 2 years of age Follow‐up: 12 months	Study population		RR 1.29 (1.16 to 1.44)	1700 (1 RCT)a	⊕⊕⊝⊝ Lowb	Integration of immunisation with other health services may increase the proportion of children who receive full vaccination by 2 years of age.
	538 per 1000	694 per 1000 (624 to 774)
Proportion of children who received the vaccine under study (BCG) Follow‐up: 12 months	Study population		RR 0.97 (0.93 to 1.01)	2089 (1 RCT)a	⊕⊕⊝⊝ Lowb	Integration of immunisation with other health services may have little or no effect in increasing the proportion of children who receive BCG.
	916 per 1000	888 per 1000 (852 to 925)
Proportion of children who received the vaccine under study (yellow fever) Follow‐up: 12 months	Study population		RR 1.13 (1.04 to 1.22)	1383 (1 RCT)a	⊕⊕⊝⊝ Lowb	Integration of immunisation with other health services may increase the proportion of children who receive yellow fever vaccine by 1 year of age.
	732 per 1000	827 per 1000 (659 to 1000)
Proportion of children who received the vaccine under study (measles) Follow‐up: 12 months	Study population		RR 1.13 (1.04 to 1.22)	1370 (1 RCT)a	⊕⊕⊝⊝ Lowb	Integration of immunisation with other health services may increase the proportion of children who receive measles vaccine.
	739 per 1000	835 per 1000 (739 to 902)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BCG: Bacille Calmette‐Guérin; CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded study is Dicko 2011. 
^bWe downgraded by two levels for serious study limitations and because there was only one study.

Summary of findings 11. Engagement of community leaders compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries.

Engagement of community leaders compared to routine care for improving coverage of childhood immunisation in low‐ and middle‐income countries
Patient or population: children under 5 years of age Setting: Nigeria Intervention: engagement of community leaders Comparison: routine care
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	Number of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with routine care	Risk with engagement of community leaders
Proportion of children who received DTP3 or Penta 3 by 1 year of age Follow‐up: 18 months	Study population		RR 1.37 (1.11 to 1.69)	2020 (1 RCT)a	⊕⊕⊕⊝ Moderateb	Engagement of community leaders probably improves the proportion of children who receive Penta 3 vaccine.
	240 per 1000	329 per 1000 (266 to 405)
Proportion of children who received all recommended vaccines by 2 years of age	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Proportion of children who received the vaccine under study (measles) Follow‐up: 18 months	Study population		RR 1.96 (1.61 to 2.39)	1227 (1 RCT)a	⊕⊕⊕⊝ Moderateb	Engagement of community leaders probably increases the proportion of children who receive measles vaccine.
	240 per 1000	470 per 1000 (386 to 573)
Proportion of children under 5 years of age fully immunised with all scheduled vaccines	‐		‐	‐	‐	None of the included studies reported this outcome.
Occurrence of vaccine‐preventable diseases	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Cost of the intervention	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
Adverse events	‐	‐	‐	‐	‐	None of the included studies reported this outcome.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; DTP: diphtheria‐tetanus‐pertussis; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aIncluded study was Oyo‐Ita 2021.
^bWe downgraded by one level because there was only one study.

Background

Infectious diseases constitute the major cause of ill health. Infants and young children are more affected because of their immature immune system (Kollmann 2017). The use of vaccination to increase herd immunity and curb the incidence of infectious diseases has been proven to be a powerful public health tool for boosting the immune system and improving child survival, not only by directly combating some of the key diseases and causes of child mortality, but also by providing a platform for broader health services (Andre 2008; Bloom 2011; CDC 1999; Clements 2008; JAMA 2006; Okwo‐Bele 2012; Wiysonge 2006). This strategy assumed a global dimension when the World Health Organization (WHO) launched the Expanded Programme on Immunization (EPI) in 1974, following the successful global smallpox eradication programme (Wiysonge 2013). When the EPI was launched, WHO recommended a standard immunisation schedule covering six basic antigens (i.e. tuberculosis (Bacille Calmette‐Guérin (BCG)), polio, diphtheria, tetanus, pertussis, and measles), which are generally referred to as traditional EPI vaccines. With the emergence of new vaccines, more killer diseases can be prevented in infancy and adolescence. These vaccines include (but are not limited to) hepatitis B (HBV), Haemophilus influenzae type b (Hib), human papillomavirus (HPV), pneumococcal conjugate, rotavirus, yellow fever, meningococcal meningitis A, Japanese encephalitis, and rubella (WHO 2012a).

The traditional EPI vaccines are estimated to prevent 2.5 million child deaths annually (mainly from measles, pertussis, tetanus, and diphtheria), as well as to prevent severe morbidity for millions more children around the world from devastating diseases such as poliomyelitis and tuberculous meningitis (CDC 1999; Liu 2012; Machingaidze 2013a; Okwo‐Bele 2011; Rainey 2011; Wiysonge 2005). However, immunisation has the potential to do more. Increasing coverage with existing vaccines, as well as the introduction and increased uptake of a portfolio of newly available vaccines in EPI programmes in low‐ and middle‐income countries (LMICs), could save the lives of millions more children each year (Andre 2008; Brown 2011; Chopra 2013; Duclos 2009; Liu 2012; Machingaidze 2013a; WHO‐UNICEF 2009; Wiysonge 2012a). Despite these huge potentials, the vaccination achievements so far have been described as 'fragile', given the outbreaks of some of these infectious diseases in LMICs (Duclos 2009; SAGE 2015; Siegfried 2010), and in high‐income countries (Dubé 2013; SAGE 2015). The outbreaks are indications of inadequate vaccination that exists in geographic, ethnic, and socioeconomic groups in the communities (Nowlan 2019). They reflect the existence of communities with partially vaccinated or unvaccinated children (Dubé 2013; SAGE 2015), whose herd immunity is inadequate to stall the transmission of these diseases.

In order to overcome these weaknesses and realise the full potential of immunisation, the 'Decade of Vaccines Collaboration' developed the Global Vaccine Action Plan (GVAP), which was endorsed by the World Health Assembly in May 2012. The plan envisions "a world in which all individuals and communities enjoy lives free from vaccine‐preventable diseases". The mission of the GVAP is to extend, by 2020 and beyond, the full benefit of immunisation to all people, regardless of where they are born, who they are, or where they live (WHO 2012a).

Description of the condition

The proportion of children who receive the full series of three doses of diphtheria‐tetanus‐pertussis containing vaccines (DTP3) by 12 months of age is traditionally used as a standard measure of the programme's ability to reach the target population, and is used as an indicator of the overall performance of EPI programmes (Okwo‐Bele 2011; WHO‐UNICEF 2009). Global DTP3 coverage hovered around 5% in 1974, when EPI was launched, and increased very slowly to 17% in 1980 (WHO 2012b). Through the 1980s, WHO and the United Nations Children's Fund (UNICEF) led an aggressive global campaign to achieve universal childhood immunisation by vaccinating at least 80% of all children with the six traditional EPI vaccines by 1990 (Machingaidze 2013a; Okwo‐Bele 2011). The global DTP3 coverage reached 76% in 1990 (WHO 2015). However, the progress in LMICs was slow as DTP3 coverage was only 57% in Africa and 70% in South‐East Asia (UNICEF 2015a). Up to 2006, only 27% of LMICs had DTP3 coverage above the 80% target (Rainey 2011). A significant improvement was reported in 2007 in LMICs, particularly in sub‐Saharan Africa and South‐East Asia, although these two regions did not reach the 80% DTP3 coverage target (Duclos 2009). The WHO and UNICEF estimated that DTP3 coverage increased to 86% globally in 2014 (WHO 2015) and dropped to 83% in 2020 (WHO 2021). By 2018, 129 countries had achieved the targeted 90% coverage of three doses of DPT (WHO 2019a), though the global coverage has stagnated in the last decade (WHO 2021).

About 19 million children under one year of age were said to be unvaccinated with DTP3 globally in 2018 (WHO 2019a). Close to 60% of these children live in just 10 LMICs in Africa and South‐East Asia: Angola, Brazil, the Democratic Republic of the Congo, Ethiopia, India, Indonesia, Nigeria, Pakistan, the Philippines, and Vietnam (WHO 2015). As a consequence of this continued failure to reach optimal immunisation coverage, 1.5 million children die each year from diseases preventable by vaccines currently recommended by WHO. These include 476,000 deaths from pneumococcal disease, 453,000 from rotavirus diarrhoea, 199,000 from Hib, 195,000 from pertussis, 118,000 from measles, and 59,000 from neonatal tetanus (WHO 2015). Factors associated with low immunisation coverage are linked to the health system, healthcare providers, and healthcare recipients (Bloom 2005; Rainey 2011; Wiysonge 2012b).

Some experts have observed growing concern about vaccines, which has influenced vaccine acceptance (Bloom 2005; Dubé 2013; Feemster 2013; Larson 2014). Vaccine acceptance spans a spectrum from complete rejection to total acceptance (Feemster 2013). Along the spectrum is an emerging phenomenon: vaccine hesitancy (Larson 2014). The Strategic Advisory Group of Experts on Immunisation (SAGE) defines vaccine hesitancy as a behaviour that includes confidence, complacency, and convenience. According to SAGE, vaccine‐hesitant people may accept all vaccines but with concerns, may accept only some vaccines or delay in taking up vaccines, or may totally reject all vaccines (Larson 2014).

There are varied reasons for failing to achieve universal coverage in different settings. Such reasons span from inaccessible services and poor logistic support to political instability, including wars and public perceptions (Bloom 2005). Evidence is required to inform strategies to reach partially vaccinated and unvaccinated people in these countries. Such strategies also need to be tailored to local issues, needs, and conditions.

Description of the intervention

Several experts have highlighted the wide range of issues affecting the uptake of vaccines in various settings (Bloom 2005; Dubé 2013; Mills 2005; Munoz 2015). The issues vary between and within settings due to social, economic, cultural, geographical, political, and religious factors. Therefore, potential interventions are also likely to vary across different settings. Based on the findings from reviews on this, Table 12 presents a matrix of interventions to address the issues. Broadly, these strategies could include recipient‐oriented interventions, for example recipient recalls and reminders, health education of clients, teaching recipients skills; provider‐oriented interventions, such as audit and feedback and chart‐based or computerised provider reminders; and health system interventions, such as outreach programmes and improved quality of delivery of care (Lewin 2011). These could be delivered as single or multi‐faceted interventions.

1. Interventions to improve vaccination uptake and how they work.

Target	Interventions	Purpose of the interventions
Recipients	Communication interventions to inform and educate targeting individuals, groups, communities or providers, or a combination of these through face‐to‐face interaction, use of mass media, printed material, etc.	To improve understanding of vaccination; its relevance; benefits and risks of vaccination; where, when, and how to receive vaccine services; and who should receive vaccine services (Willis 2013)
	Communication interventions to recall or remind using face‐to‐face interaction, telephone, mail, etc.	To remind those who are overdue for vaccination in order to reduce the dropout rate (Willis 2013)
	Communication interventions to teach skills, e.g. parenting skills	To provide people with the ability to operationalise knowledge through the adoption of practical skills (Willis 2013)
	Communication interventions to provide support	To provide assistance or advice for consumers (Willis 2013)
	Interventions to facilitate decision‐making, e.g. decision aids on vaccination for parents	To assist carers in participating in decision‐making (Dubé 2013)
	Interventions to enable communication through traditional media, internet, etc.	To make communication possible (Dubé 2013)
	Interventions, including communication, to enhance community ownership, e.g. community dialogues involving traditional and religious rulers	To increase demand for vaccination To ensure sustainability To build trust in vaccination and vaccination services To drive demand for vaccination
	Incentives	To reward service uptake; to cover out‐of‐pocket costs
Providers	Training	To improve knowledge about vaccination, to improve skills, to improve attitudes to clients, to reduce missed opportunities for vaccination
	Audit and feedback	To ensure quality and client satisfaction with services
	Supportive supervision	To ensure quality and maintain standards, to reduce missed opportunities for vaccination
	Incentives	To boost morale and enhance performance
Health system	Infrastructural development, e.g. provision of health facilities, provision of road to improve access to health facilities	To ensure access to services
	Logistic support	To improve service quality and so improve utilisation to ensure availability of services
	Service delivery, e.g. outreach; home visits; integration of vaccination with other services; guidelines/protocol for vaccination; increased resources	Outreach to improve access to services Home visits to remind parents about vaccination and identify unimmunised children for immunisation Integration to encourage vaccine uptake Guidelines and protocols to ensure quality of services Improved resources to ensure availability of services
Policy‐makers	Advocacy for: development of supporting policies, increased funding of health services	To promote the development of policies to support vaccine uptake To increase funding to the health sector

These interventions have been revolutionised with the advent of digital technology. Digital technology is defined as the use of the Internet, mobile phones, etc. to collect, store, and analyse information digitally (WB 2016). When applied in the health system to achieve health outcomes, it is termed digital health. In line with the WHO definition of digital health (WHO 2019b), we define digital intervention for childhood vaccination as any digital technology that is applied to improve childhood immunisation coverage and is implemented within digital health applications and information and communications technology systems. Table 13 shows the digital interventions identified by the WHO for health care delivery (WHO 2019b).

2. WHO Classification of Digital Interventions.

1.0 Clients

1.1 Targeted client communication

1.1.1 Transmit health event alerts to specific population group(s)

1.1.2 Transmit targeted health information to client(s) based on health status or demographics

1.1.3 Transmit targeted alerts and reminders to client(s)

1.1.4 Transmit diagnostics result, or availability of result, to client(s)

1.2 Untargeted client communication

1.2.1 Transmit untargeted health information to an undefined population

1.2.2 Transmit untargeted

1.3 Client to client communication

1.3.1 Peer group for clients

1.4 Personal health tracking

1.4.1 Access by client to own medical records

1.4.2 Self monitoring of health or diagnostic data by client 1.4.3 Active data capture/ documentation by client

1.4.3 Active data capture/ documentation by client

1.5 Citizen‐based reporting

1.5.1 Reporting of health system feedback by clients

1.5.2 Reporting of public health events by clients

1.6 On‐demand information services to clients

1.6.1 Client look‐up of health information

1.7 Client financial transactions

1.7.1 Transmit or manage out‐of‐pocket payments by client(s)

1.7.2 Transmit or manage vouchers to client(s) for health services

1.7.3 Transmit or manage incentives to client(s) for health services

2.0 Health workers

2.1 Client identification and registration

2.1.1 Verify client unique identity

2.1.2 Enrol client for health services/clinical care plan

2.2 Client health records

2.2.1 Longitudinal tracking of clients’ health status and services

2.2.2 Manage client’s structured clinical records

2.2.3 Manage client’s unstructured clinical records

2.2.4 Routine health indicator data collection and management

2.3 Health worker decision support

2.3.1 Provide prompts and alerts based according to protocol

2.3.2 Provide checklist according to protocol

2.3.3 Screen clients by risk or other health status

2.4 Telemedicine

2.4.1 Consultations between remote client and health worker

2.4.2 Remote monitoring of client health or diagnostic data by provider

2.4.3 Transmission of medical data to health worker

2.4.4 Consultations for case management between health worker(s)

2.5 Health worker communication

2.5.1 Communication from health worker(s) to supervisor

2.5.2 Communication and performance feedback to health worker(s)

2.5.3 Transmit routine news and workflow notifications to health worker(s)

2.5.4 Transmit non‐routine health event alerts to health worker(s)

2.5.5 Peer group for health workers

2.6 Referral co‐ordination

2.6.1 Coordinate emergency response and transport

2.6.2 Manage referrals between points of service within health sector

2.6.3 Manage referrals between health and other sectors

2.7 Health worker activity planning and scheduling

2.7.1 Identify client(s) in need of services

2.7.2 Schedule health worker's activities

2.8 Health worker training

2.8.1 Provide training content to health worker(s)

2.8.2 Assess capacity of health worker(s)

2.9 Prescription and medication management

2.9.1 Transmit or track prescription orders

2.9.2 Track client's medication consumption

2.9.3 Report adverse drug events

2.10 Laboratory and Diagnostics Imaging Management

2.10.1 Transmit diagnostic result to health worker

2.10.2 Transmit and track diagnostic orders

2.10.3 Capture diagnostic results from digital devices

2.10.4 Track biological specimens

3.0 Health system managers

3.1 Human resource management

3.1.1 List health workforce cadres and related identification information

3.1.2 Monitor performance of health worker(s)

3.1.3 Manage certification/registration of health worker(s)

3.1.4 Record training credentials of health worker(s)

3.2 Supply chain management

3.2.1 Manage inventory and distribution of health commodities

3.2.2 Notify stock levels of health commodities

3.2.3 Monitor cold‐chain sensitive commodities

3.2.4 Register licensed drugs and health commodities

3.2.5 Manage procurement of commodities

3.2.6 Report counterfeit or substandard drugs by clients

3.3 Public health event notification

3.3.1 Notification of public health events from point of diagnosis

3.4 Civil Registration and Vital Statistics

3.4.1 Notify birth event

3.4.2 Register birth event

3.4.3 Certify birth event

3.4.4 Notify death event

3.4.5 Register death event

3.4.6 Certify death event

3.5 Health financing

3.5.1 Register and verify client insurance membership

3.5.2 Track insurance billing and claims submission

3.5.3 Track and manage insurance reimbursement

3.5.4 Transmit routine payroll payment to health worker(s)

3.5.5 Transmit or manage incentives to health worker(s)

3.5.6 Manage budget and expenditures

3.6 Equipment and asset management

3.6.1 Monitor status of health equipment

3.6.2 Track regulation and licensing of medical equipment

3.7 Facility management

3.7.1 List health facilities and related information

3.7.2 Assess health facilities

4.0 Data services

4.1 Data collection, management, and use

4.1.1 Non‐routine data collection and management

4.1.2 Data storage and aggregation

4.1.3 Data synthesis and visualisation

4.1.4 Automated analysis of data to generate new information or predictions on future events

4.2 Data coding

4.2.1 Parse unstructured data into structured data

4.2.2 Merge, de‐duplicate, and curate coded datasets or terminologies

4.2.3 Classify disease codes or cause of mortality

4.3 Location mapping

4.3.1 Map location of health facilities/structures

4.3.2 Map location of health events

4.3.3 Map location of clients and households

4.3.4 Map location of health worker

4.4 Data exchange and interoperability

4.4.1 Data exchange across systems

Excerpt from WHO 2019b.

How the intervention might work

The various interventions serve different purposes; Table 12 presents this matrix. Interventions that target recipients include communication to inform and educate, recall/remind about immunisation that is due or missed, teach skills, provide support, facilitate decision‐making, enhance community ownership, and incentivise. These interventions aim to increase the demand for vaccination. Provider‐oriented interventions include training of health providers, audit and feedback, supporting supervision, and incentivising them. They improve the knowledge and skills of the health providers, and ensure quality and clients’ satisfaction. Health system interventions promote access to services and support the supply of services. They include infrastructural development, logistic support, and modalities of service delivery. Some interventions can be used for both recipients and providers, for example remind/recall interventions could target both caregivers and healthcare providers. Policy interventions include policies to boost vaccine uptake and funding of vaccination.

Most of these interventions can be digitalised. Digital interventions work through devices that can access the Internet. The use of the Internet tripled between 2005 and 2015, with 70% of the poorest in developing countries owning mobile phones (WB 2016). This has the prospect of improving vaccination service delivery.

Why it is important to do this review

In many LMICs, immunisation coverage is low (UNICEF 2015b; WHO 2012b), routine immunisation systems are weak (Machingaidze 2013a), and community knowledge of immunisation is low (Zipursky 2010). The target of GVAP was to achieve DTP3 coverage of at least 90% in all countries by 2015. While 129 countries achieved the 90% coverage target by 2014, the 10 countries with the largest numbers of unimmunised children are all low‐income or lower‐ to middle‐income countries (SAGE 2015; WHO 2015).

Making well‐informed decisions about how best to achieve and sustain high and equitable immunisation coverage in these countries will depend partly on decision‐makers accessing the best scientific evidence about what interventions work, and integrating this evidence into their national health systems (Lewin 2008). One previous Cochrane Review assessed recipient‐oriented reminders and recalls (Jacobson Vann 2018). The evidence indicated that reminding people to receive vaccinations through postcards, letters, or telephone calls increased immunisation uptake. Client reminder/recall can also be achieved through the use of child immunisation cards, wearables (for example, pendants, bracelets), and digital devices like powered digital pendants and vaccine indicator reminders. This strategy generally relies, in some cases, on setting up an efficient computerised vaccination registry or other practice‐based information systems to track clients' vaccination status and eligibility for recommended vaccines, and also an efficient communication system to send reminders to clients. These technologies were considered lacking in many LMICs. However, with the increase in internet penetration into remote communities, it is not known how effective these technologies could be in LMICs. This review explores client‐oriented interventions, provider‐oriented interventions (Djibuti 2009), and health system interventions (Brugha 1996), aiming towards improving immunisation coverage.

This is the second update of the Cochrane Review published in 2011 (Oyo‐Ita 2011), and complements two other Cochrane Reviews conducted under the auspices of the 'Communicate to Vaccinate' project (Lewin 2011), which have a global focus and assess the effects of face‐to‐face (Kaufman 2013) and community‐directed interventions (Saeterdal 2014) to inform or educate about childhood vaccination. It also complements Jacobson Vann's review on client reminder and recall systems to improve immunisation rates (Jacobson Vann 2018). Included in this review update is the application of digital technologies at the client, health provider, and health system levels to improve vaccine uptake in LMICs.

Objectives

To evaluate the effectiveness of intervention strategies to boost demand and supply of childhood vaccines, and sustain high childhood immunisation coverage in low‐ and middle‐ income countries.

Methods

Criteria for considering studies for this review

Types of studies

We included the following.

1. Randomised controlled trials (RCTs), with randomisation at either individual or cluster level. For cluster‐RCTs, we only included those with at least two intervention and two control clusters.

2. Non‐randomised controlled trials (nRCTs), with allocation at either individual or cluster level. We included studies that allocated by alternation between groups, by the use of birth dates or weekdays, or by other non‐random methods. For cluster trials, we only included those with at least two intervention and two control clusters.

3. Interrupted time series studies (ITS) and repeated measures studies, with a clearly defined time point when the intervention occurred and at least three data points before and three after the intervention.

4. Controlled before‐after (CBA) studies with a minimum of two intervention and two control sites, comparable timing of the periods of study for the control and intervention groups, and comparability of the intervention and control groups on key characteristics.

We excluded CBA studies, cluster‐RCTs, and nRCTs that had only two study locations, in accordance with the Cochrane Effective Practice and Organisation of Care (EPOC) criteria for inclusion of studies (EPOC 2015a).

Types of participants

Studies conducted in LMICs (World Bank 2016), which included:

1. children under five years of age receiving WHO‐recommended vaccines through routine childhood immunisation services;

2. caregivers of children who were receiving vaccines through routine childhood immunisation services;

3. healthcare workers administering vaccines through routine childhood immunisation services;

4. health systems that deliver immunisation services;

5. communities/community leaders; or

6. a combination of these.

For the purpose of this review, we defined routine childhood immunisation services as regularly scheduled immunisation services to children under five years of age, whether these services were offered at healthcare facilities, at fixed outreach sites, or by mobile health teams in communities (Machingaidze 2013b).

We limited the review to LMICs because of the continued failure to meet immunisation targets and the weak routine immunisation system in this setting.

Types of interventions

Interventions

1. Recipient‐oriented interventions, for example:

   1. interventions to improve communication about childhood immunisation, including to inform or educate, provide support, facilitate decision‐making, enable communication (Willis 2013);

   2. recipient incentives;

   3. enhance community ownership;

   4. promote vaccination as a requirement for school entry;

   5. remind recipient (caregivers) of vaccination appointment/schedule.

2. Provider‐oriented interventions, for example:

   1. any intervention to reduce missed opportunities for childhood vaccination (e.g. audit and feedback, provider reminders, supportive supervision);

   2. health education, training, and refresher courses for providers;

   3. incentives to health providers.

3. Health system interventions, for example:

   1. interventions to enhance supply chain management, such as the provision of a reliable cold chain system provision of transport for vaccination, vaccine stock management;

   2. outreach programmes (e.g. school immunisation outreach programmes, door‐to‐door canvassing (channelling);

   3. expanded services (e.g. extended hours for immunisation);

   4. increases in budgets for immunisation;

   5. integration of immunisation services with other services;

   6. plans of action for immunisation coverage and disease reduction goals;

   7. use of digital technology for record keeping and tracking of clients for vaccination.

4. Communities/community leaders:

   1. involving community/community leaders to support vaccination activities.

5. Multi‐faceted (i.e. any combination of the above categories of interventions).

6. Other interventions intended to improve immunisation coverage.

Comparisons

1. Standard immunisation practices in the study setting.

2. Different interventions, or similar interventions implemented with different degrees of intensity.

Types of outcome measures

Primary outcomes

1. Proportion of children who received DTP3 or Penta 3 by one year of age.

2. Proportion of children who received all recommended vaccines by two years of age.

For the primary outcomes, we prioritised the proportion of children who received all recommended vaccines (were fully immunised) rather than the proportion of unvaccinated children. This was because improving the number of fully vaccinated children will impact on herd immunity and interrupt the transmission of the relevant childhood diseases.

Secondary outcomes

1. Proportion of children who received the vaccine under study (excluding earlier doses of multiple dose vaccines).

2. Proportion of children under five years of age fully immunised with all scheduled vaccines.

3. Occurrence of vaccine‐preventable diseases.

4. Costs of the intervention.

5. Attitudes of caregivers and clients towards immunisation.

6. Adverse events.

Search methods for identification of studies

Electronic searches

We placed no language or date restrictions on the search strategy. We translated the MEDLINE (Ovid) search strategy into the other databases using the appropriate controlled vocabulary.

We searched the following electronic databases on the dates indicated:

• Cochrane Central Register of Controlled Trials (CENTRAL 2022, Issue 3), part of Cochrane Library, Wiley (www.cochranelibrary.com/) (searched 11 July 2022);

• Ovid MEDLINE(R) ALL 1946 to 8 July 2022 (searched 11 July 2022);

• CINAHL 1981 to present, EbscoHost (searched 11 July 2022);

• Global Index Medicus, World Health Organization (WHO) (www.globalindexmedicus.net/) (searched 11 July 2022);

• Embase 1980 to 2014 Week 34, Ovid (searched 2 September 2014);

• LILACS, Virtual Health Library (VHL) (searched 9 February 2014);

• Sociological Abstracts 1952 to current, ProQuest (searched 9 February 2014).

Searches of Embase, Sociological Abstracts, and LILACS were last run in 2014 as none of the 14 included studies not indexed in MEDLINE at that point were indexed in any of these databases. All of the search strategies used are in Appendix 1.

Searching other resources

We searched the following trials registries:

• World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) (www.who.int/ictrp/en/) (searched 11 July 2022);

• ClinicalTrials.gov, US National Institutes of Health (NIH) (clinicaltrials.gov/) (searched 11 July 2022).

In addition to the electronic searches above, we:

• screened reference lists of relevant systematic reviews for potentially eligible studies: Atkinson 2019; Balzarini 2020; Batt 2004; Bordley 2000; Frascella 2020; Glenton 2011; Harvey 2015; Jacobson Vann 2018; Johri 2015b; Kaufman 2013; Kendrick 2000; Lagarde 2009; Mekonnen 2019; Odone 2015; Pegurri 2005; Ryman 2008;Saeterdal 2014;

• screened reference lists of included studies for potentially eligible studies.

We carried out a citation search for 14 of the included studies in Science Citation Index and Social Sciences Citation Index, 1975 to present; Emerging Sources Citation Index 2015 to present, Web of Science Core Collection (searched 19 February 2020): Andersson 2009; Banerjee 2010; Barham 2005; Bolam 1998; Chen 2016; Dicko 2011; Djibuti 2009; Maluccio 2004; Morris 2004; Owais 2011; Pandey 2007; Robertson 2013; Usman 2009; Usman 2011.

Data collection and analysis

Selection of studies

At least two review authors independently screened the titles and abstracts of papers identified in the search output for potentially eligible studies. We retrieved the full texts of potentially eligible studies for further assessment, and two review authors independently applied the inclusion criteria to these publications. We resolved disagreements about the inclusion of studies through discussion and consensus between the two review authors, and involved a third review author if the disagreement was not resolved. We obtained methodological advice from the EPOC editorial base for unresolved issues. The Characteristics of excluded studies presents reasons for excluding studies.

Data extraction and management

The review data extraction form was developed by AO and reviewed by all the authors. Paired review authors independently carried out data extraction and risk of bias assessment. We resolved disagreements in data extraction by consensus between two review authors, with arbitration by a third author (MM) as required. The data extracted into an Excel spreadsheet included the following.

1. Setting of the study.

2. Type of study: distinguishing between individual RCTs, cluster‐RCTs, nRCTs, CBA studies, and ITS studies.

3. Type of participants: children, caregivers, community members, and providers.

4. Type of interventions: categorised into participant and community, provider, health system, and multi‐faceted.

5. Types of outcomes measured: data on outcome measures such as the proportion of children immunised with different antigens.

Assessment of risk of bias in included studies

Two review authors (AO and OO) applied the EPOC risk of bias criteria for RCTs, nRCTs, CBAs, and ITS studies to determine the risk of bias in included studies (EPOC 2015b). We resolved disagreements by discussion and consensus, with arbitration by a third review author (MM) as required.

Each criterion was scored as 'low risk', 'unclear risk', or 'high risk' (Characteristics of included studies table). Figure 1 and Figure 2 present the risk of bias for each included study. We considered a study as having a 'low risk of bias' if all criteria prescribed by EPOC were scored as 'yes'; 'unclear risk of bias' if one or more criteria were scored as 'unclear'; and 'high risk of bias' if one or more key criteria were scored as 'no'. The key criteria included random allocation, blinding of outcome assessors, completeness of outcome data, and protection against contamination for RCTs and nRCTs; and independence of intervention from other changes, possibility of intervention affecting data collection, completeness of outcome data, and blinding of outcome assessors for ITS studies.

1.

Risk of bias summary: review authors' judgements about each methodological quality item for each included study.

2.

Risk of bias graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.

Measures of treatment effect

We used the risk ratio (RR) for dichotomous data. If studies reported odds ratios (ORs), we converted the estimates to risk ratios following guidance from section 6.4.1.1 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2023). We planned to calculate the mean difference (MD) for costs and any other analysis of continuous data, but none of the included studies reported these types of data. We reported 95% confidence intervals (CI) for all measures.

Unit of analysis issues

Twenty of the included studies were cluster‐RCTs (Andersson 2009; Banerjee 2010; Barham 2005; Basinga 2011; Brugha 1996; Chen 2016; Dicko 2011; Djibuti 2009; Engineer 2016; Gibson 2017; Habib 2017; Maldonado 2020; Maluccio 2004; Morris 2004; Nagar 2018; Oyo‐Ita 2021; Pandey 2007; Robertson 2013; Uddin 2016; Wallace 2019). We included cluster‐RCTs in the meta‐analysis after making adjustments for the design effect using standard procedures (Rao 1992). An estimate for the intra‐cluster correlation (ICC) or design effect was reported (or could be calculated) in Andersson 2009; Banerjee 2010; Dicko 2011; Engineer 2016; Habib 2017; Maldonado 2020; Morris 2004; Nagar 2018; Uddin 2016; and Wallace 2019. We used these estimates of the ICC to adjust the standard error for the data for Andersson 2009; Barham 2005; Brugha 1996; Chen 2016; Dicko 2011; Habib 2017; Maluccio 2004; Morris 2004; Nagar 2018; Robertson 2013; Sengupta 2017; and Uddin 2016, based on similar settings or nearby countries. For example, Pandey 2007 (India) was adjusted using Banerjee 2010 (India), Barham 2005 (Mexico) and Maluccio 2004 (Nicaragua) were adjusted using Morris 2004 (Honduras), and Brugha 1996 (Ghana) was adjusted using Dicko 2011 (Mali).

We entered data from these studies as absolute figures into Review Manager 5.4 (Review Manager 2020) and calculated RRs; consequently, we applied the ICC to adjust for the cluster effect. The adjusted standard error (SE) of (log RR) for the cluster‐RCT studies was inserted in the analysis.

Dealing with missing data

We judged studies with missing outcome data as having a high risk of bias (see Risk of bias in included studies), where we thought missingness in the outcome was dependent on the intervention group and the true value of the outcome. However, we did not conduct intention‐to‐treat analysis or data imputation for studies with missing outcome data.

We contacted the authors of two studies to obtain missing data (Djibuti 2009; Morris 2004). Morris 2004 responded, and we used the additional data to estimate the ICC for the study. Additional data received included the absolute number of events in each arm of the study for the Morris 2004 study; we estimated the ICC for mumps, measles, rubella (MMR) (0.013), and DTP1 (0.0377) for the post‐intervention assessment only. We entered the raw data into RevMan 5.4 to estimate the RR. We then used the ICC to adjust the standard error for the two outcomes from this study that we included in this review.

Fifteen studies had independent sampling at pre‐ and post‐intervention (Andersson 2009; Barham 2005; Basinga 2011; Brugha 1996;Chen 2016; Dicko 2011; Djibuti 2009; Habib 2017; Kazi 2018; Maluccio 2004; Morris 2004; Oyo‐Ita 2021; Robertson 2013; Sengupta 2017; Uddin 2016). There were no missing data in nine studies (Amare 2021; Bangure 2015; Basheer 2021; Dissieka 2019; Kawakatsu 2020; Linkins 1994; Siddiqi 2020; Usman 2009; Usman 2011). Intention‐to‐treat analysis was done for five studies (Domek 2016; Ekhaguere 2019; Engineer 2016; Nagar 2018; Wallace 2019). Eleven studies analysed data per protocol (Banerjee 2010; Bolam 1998; Domek 2019; Gibson 2017; Hu 2017; Maldonado 2020; Murthy 2019; Owais 2011; Pandey 2007; Powell‐Jackson 2018; Todd 2010). One study had uncertain status on loss to follow‐up (Oladepo 2021).

Assessment of heterogeneity

We reviewed heterogeneity in the setting, interventions, and outcomes of the included studies in order to make a qualitative assessment of the extent to which the included studies were similar to each other. We considered meta‐analyses with either Chi² P < 0.1 or I² ≥ 0.5 to have substantial statistical heterogeneity. We planned to subject such meta‐analyses to subgroup analyses for exploration of heterogeneity (see Subgroup analysis and investigation of heterogeneity). Two subgroup analyses were feasible: community‐ or facility‐based health education, and setting of study (urban versus rural).

Assessment of reporting biases

Testing for asymmetry with a funnel plot was not feasible because the number of included studies for meta‐analysis was too low.

Data synthesis

We planned to pool data from studies with similar interventions (participant or community, provider, health system, multi‐faceted), grouped by study design (RCTs, nRCTs, CBAs, ITS studies), in a meta‐analysis using the random‐effects model. For studies that reported only effect estimates with the measures of uncertainty, but without numbers of participants and numbers of events, we planned to analyse the effect estimate using the generic inverse variance approach. ITS studies were to be reported as changes in level and slope. We selected the random‐effects model as the default procedure in the analysis due to heterogeneity, based on the assumption of random distribution of the variation in the effects of interventions in the different studies.

Subgroup analysis and investigation of heterogeneity

We planned to explore anticipated differences in the impact of interventions across settings and mode of delivery of the interventions. We planned the following subgroup analyses.

1. Setting of the study (rural, urban).

2. Individual or group intervention.

3. Single or multi‐faceted/integrated intervention.

4. Conditional or non‐conditional incentive.

5. Facility‐ or community‐based intervention.

6. Comparison with routine or another intervention.

7. Quasi‐RCT or RCT.

Due to the paucity of data, subgroup analysis was only possible for health education and phone/SMS interventions.

Sensitivity analysis

We planned to perform a sensitivity analysis based on risk of bias and missing data. Available data were, however, insufficient to perform this analysis. We extracted data for 12 interventions. Only health education, phone/SMS, and home‐based records had three studies and above; the others had one to two studies included.

We observed heterogeneity in health education for DTP3 and measles, home‐based records only and home‐based records + health education for DTP3, phone/SMS DTP3, full vaccination, Bacille Calmette‐Guérin, and measles vaccine uptake and regular immunisation for full vaccination. This could be attributed to the high risk of bias of the included studies and the difference in the mode of delivery of the interventions. Location was shown to contribute to heterogeneity with phone/SMS for DTP3 uptake. We presented data with statistical heterogeneity above 95% as a narrative.

Summary of findings and assessment of the certainty of the evidence

We created 11 summary of findings (SoF) tables comparing various interventions to routine care or placebo for key outcomes:

• proportion of children who received DTP3/Penta 3 by one year of age;

• proportion of children who received all recommended vaccines by two years of age;

• proportion of children who received the vaccine under study (BCG);

• proportion of children who received the vaccine under study (OPV3);

• proportion of children who received the vaccine under study (HBV3);

• proportion of children who received the vaccine under study (measles vaccine);

• proportion of children who received other vaccine under study (BCG + DTP3 + OPV);

• received at least one vaccine;

• proportion of children under five years of age fully immunised with all scheduled vaccines;

• occurrence of vaccine‐preventable diseases;

• cost of the intervention ‐ reported as a narrative in two studies;

• adverse events.

The findings are presented in Table 1; Table 2; Table 3; Table 4; Table 5; Table 6; Table 7; Table 8; Table 9; Table 10; Table 11.

Two review authors (AO and OO) assessed the certainty of the evidence (or confidence in the estimates) using the GRADE approach (Guyatt 2008; Higgins 2023). We entered data for key interventions into the GRADEpro GDT software and assessed the certainty of evidence for each outcome against five criteria: risk of bias, consistency, precision, publication bias, and directness. We judged the certainty of evidence for the outcomes reported by RCTs as 'high', or downgraded to 'moderate', 'low', or 'very low', following the identification of deficiencies that decreased our confidence in the effect estimates. The implications of these judgements are explained below.

High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low certainty: our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect.
Very low certainty: we have very little confidence in the effect estimate. The true effect is likely to be substantially different from the estimate of effect.

'Substantially different' implies a large enough difference that it might affect a decision.

Results

Description of studies

Results of the search

For this update, the electronic and supplementary searches yielded 16,478 records with 14,133 selected after duplicates were dropped. The number of full‐text articles screened for eligibility was 129: we excluded 88 with reasons (see Characteristics of excluded studies), and four are awaiting assessment (see Characteristics of studies awaiting classification). We included 27 new studies in this update and there are now 41 studies included in the review. The additional 27 studies included in this second update are: Amare 2021; Bangure 2015; Basheer 2021; Basinga 2011; Chen 2016; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Engineer 2016; Gibson 2017; Habib 2017; Hu 2017; Kawakatsu 2020; Kazi 2018; Linkins 1994; Maldonado 2020; Murthy 2019; Nagar 2018; Oladepo 2021; Oyo‐Ita 2021; Powell‐Jackson 2018; Sengupta 2017; Siddiqi 2020; Todd 2010; Uddin 2016; Wallace 2019. Six of the included studies are presented as narrative reports (Amare 2021; Basinga 2011; Djibuti 2009; Engineer 2016; Murthy 2019; Todd 2010). The stage‐wise study selection process is presented in the PRISMA flow diagram (Figure 3).

3.

Study flow diagram.

Included studies

Study design and setting

Forty‐one studies met the inclusion criteria. We have described these studies in the Characteristics of included studies section. Twenty of the included studies were cluster‐RCTs (Andersson 2009; Banerjee 2010; Barham 2005; Basinga 2011; Brugha 1996; Chen 2016; Dicko 2011; Djibuti 2009; Engineer 2016; Gibson 2017; Habib 2017; Maldonado 2020; Maluccio 2004; Morris 2004; Nagar 2018; Oyo‐Ita 2021; Pandey 2007; Robertson 2013; Uddin 2016; Wallace 2019). Of these, Brugha 1996, Chen 2016, and Robertson 2013 were matched cluster‐RCTs; Djibuti 2009 used stratified cluster sampling. Fifteen studies were individually randomised controlled trials (Bangure 2015; Bolam 1998; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Hu 2017; Kawakatsu 2020; Kazi 2018; Owais 2011; Powell‐Jackson 2018; Siddiqi 2020; Todd 2010; Usman 2009; Usman 2011). The remaining six studies were quasi‐randomised studies (Amare 2021; Basheer 2021; Linkins 1994; Murthy 2019; Oladepo 2021; Sengupta 2017). The unit of analysis was the participant in all studies except Morris 2004 and Pandey 2007, in which the household was the unit of analysis. There were no CBAs or ITS studies among the included studies. The cluster‐RCTs were adjusted for cluster effects.

Location of studies

The studies were conducted in Afghanistan (Engineer 2016; Todd 2010), China (Chen 2016; Hu 2017), Côte d'Ivoire (Dissieka 2019), Ethiopia (Amare 2021), Georgia (Djibuti 2009; Linkins 1994), Ghana (Brugha 1996), Guatemala (Domek 2016; Domek 2019), Honduras (Morris 2004), India (Banerjee 2010; Murthy 2019; Nagar 2018; Pandey 2007; Powell‐Jackson 2018; Sengupta 2017; Uddin 2016), Indonesia (Wallace 2019), Kenya (Gibson 2017; Maldonado 2020), Mali (Dicko 2011), Mexico (Barham 2005), Nepal (Bolam 1998), Nicaragua (Maluccio 2004), Nigeria (Basheer 2021; Ekhaguere 2019; Oladepo 2021; Oyo‐Ita 2021), Pakistan (Andersson 2009; Habib 2017; Kazi 2018; Owais 2011; Siddiqi 2020; Usman 2009; Usman 2011), Rwanda (Basinga 2011), and Zimbabwe (Bangure 2015; Robertson 2013).

Study participants

The age of children studied varied between studies. Kazi 2018 studied children less than two weeks of age. Dissieka 2019, Ekhaguere 2019, Gibson 2017, and Owais 2011 studied children less than six weeks of age. Bolam 1998, Domek 2016, Usman 2009, and Usman 2011 studied children within the range of zero to 14 weeks. Banerjee 2010, Domek 2019, and Nagar 2018 included children aged from birth to six months and six weeks to six months, respectively. Amare 2021, Hu 2017, Maldonado 2020, Murthy 2019, Oladepo 2021, Pandey 2007; Todd 2010, Uddin 2016, and Wallace 2019 studied children under one year. Children under two years were included in the studies by Andersson 2009, Barham 2005, Basheer 2021, Brugha 1996, Chen 2016, Dicko 2011, Engineer 2016, Kawakatsu 2020, Linkins 1994, Maluccio 2004, Morris 2004, Oyo‐Ita 2021, Sengupta 2017, and Siddiqi 2020. Basinga 2011, Habib 2017, and Robertson 2013 studied children under the age of five years. Hu 2017, Powell‐Jackson 2018, and Sengupta 2017 included children under three years of age.

Recipients of the interventions

Recipients in five studies were adults: primary healthcare workers (Amare 2021; Basheer 2021; Djibuti 2009), the general population (Andersson 2009; Pandey 2007), pregnant women (Hu 2017; Morris 2004), and mothers in the immediate post‐partum period (Bolam 1998). Others targeted mothers or caretakers of the children at home. Oyo‐Ita 2021 targeted traditional and religious leaders, health workers, and the Ward Development Committee.

Sampling

Fifteen studies carried out independent sampling in the pre‐ and post‐intervention periods (Andersson 2009; Barham 2005; Basinga 2011; Brugha 1996; Chen 2016; Dicko 2011; Djibuti 2009; Habib 2017; Kazi 2018; Maluccio 2004; Morris 2004; Oyo‐Ita 2021; Robertson 2013; Uddin 2016; Sengupta 2017). The remaining 26 studies followed up the same participants.

Source of data

The included studies varied in their sources of data on the immunisation status of the children. Six studies obtained their data from the child health card only (Kawakatsu 2020; Kazi 2018; Morris 2004; Murthy 2019; Oladepo 2021; Owais 2011). Recall and card were used in 11 studies (Banerjee 2010; Basheer 2021; Brugha 1996; Chen 2016; Dicko 2011; Gibson 2017; Habib 2017; Maluccio 2004; Oyo‐Ita 2021; Powell‐Jackson 2018; Uddin 2016). In the Gibson 2017 study, data obtained from recall were excluded from analysis and considered as loss to follow‐up. Habib 2017 reported seeing very few cards, thereby implying that data obtained were mostly from recall. One study used only recall (Andersson 2009). Data were obtained from the digital database and clinic register in 10 studies (Amare 2021; Bangure 2015; Dissieka 2019; Domek 2019; Ekhaguere 2019; Hu 2017; Linkins 1994; Nagar 2018; Siddiqi 2020; Wallace 2019). The source of data was unclear in 11 studies (Barham 2005; Basinga 2011; Bolam 1998; Djibuti 2009; Domek 2016; Engineer 2016; Pandey 2007; Robertson 2013; Sengupta 2017; Todd 2010; Usman 2009; Usman 2011).

Interventions

The individual studies evaluated interventions as follows.

1. Recipient‐oriented interventions.

   1. Health education to improve maternal knowledge on vaccination, cost and benefits of immunisation, importance of completion of the immunisation schedule, and other vaccination‐related issues (Andersson 2009; Banerjee 2010; Bolam 1998; Hu 2017; Owais 2011; Pandey 2007; Powell‐Jackson 2018; Todd 2010; Usman 2009; Usman 2011).

   2. Community mobilisation to facilitate demand for care (Habib 2017; Maldonado 2020).

   3. Recall and reminder for child vaccination including use of digital technology ‐ SMS reminders and voice messaging, redesigned vaccination cards (Bangure 2015; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Gibson 2017; Kawakatsu 2020; Kazi 2018; Linkins 1994; Murthy 2019; Nagar 2018; Oladepo 2021; Siddiqi 2020; Uddin 2016; Usman 2009; Usman 2011; Wallace 2019).

   4. Digital tracking of children (Chen 2016).

   5. Incentives to increase demand for preventive healthcare interventions.

      1. Conditional and unconditional cash transfers to encourage clinic attendance for child development services (Barham 2005; Maluccio 2004; Morris 2004; Robertson 2013).

2. Provider‐oriented interventions.

   1. Training of immunisation district managers, together with supportive supervision and audit and feedback regarding solving problems with immunisation services (Djibuti 2009).

   2. Training of health providers on valid doses for vaccination.

   3. Development of supportive supervision and mentorship guidelines and training of health workers on how to coach, mentor, effectively communicate, and conduct performance planning (Amare 2021).

   4. Training on interpersonal communication (IPC) (Basheer 2021).

3. Health system‐oriented interventions.

   1. Home visits to identify unimmunised children (Brugha 1996).

   2. Immunisation outreach sessions in the villages to ensure regular availability of immunisation services (Banerjee 2010; Habib 2017; Sengupta 2017).

   3. Integration of immunisation with intermittent preventive treatment of malaria to support child health interventions (Dicko 2011).

   4. Funding of the health system ‐ pay for performance (Basinga 2011; Engineer 2016).

   5. Community participation the establishment of immunisation camps with community leaders (Sengupta 2017).

4. Multi‐faceted interventions.

   1. Recipient‐oriented plus recipient‐oriented intervention (Bangure 2015; Usman 2009; Usman 2011; Wallace 2019).

   2. Provider‐oriented plus recipient‐oriented approach (Oyo‐Ita 2021).

   3. Health system plus recipient‐oriented interventions (Banerjee 2010; Habib 2017).

   4. Health system plus provider‐oriented plus interventions (Morris 2004).

See below for more details about these interventions.

Recipient‐oriented interventions

Community‐based health education

Health education interventions included evidence‐based discussions in the community on the prevalence of measles among children and the importance of childhood immunisation in Pakistan (Andersson 2009); face‐to‐face education of mothers in their homes on the benefits of DPT vaccination and consequences in terms of morbidity and mortality (Powell‐Jackson 2018); an information campaign in India that involved presentation of audiotape messages, and distribution of posters and leaflets in the community (Pandey 2007); and three targeted pictorial messages regarding vaccines administered by trained lay/community health workers at the mothers' homes in Pakistan (Owais 2011). The first key pictorial message highlighted how vaccines save children's lives. The second message provided logistic information about the address and location of the local vaccination centres. The third key message emphasised the significance of retaining immunisation cards, and the role they could play at the time of the child's school admissions. A copy of these pictorial messages was left with the mother. In another study, community health volunteers conducted group‐based health education to support women in the first 1000 days after delivery (Maldonado 2020).

Facility‐based health education

Three studies in Nepal and Pakistan provided health education in the health facility on the importance of completion of the immunisation schedule (Bolam 1998; Usman 2009; Usman 2011). In the Bolam 1998 study in Nepal, one arm had only one‐to‐one facility‐based education after delivery and before discharge from the hospital, the second arm had only a one‐to‐one education session in the mothers' homes three months after delivery, while the third arm included both one‐to‐one health education immediately after birth and three months later. The last arm was included in the study. The Hu 2017 study provided prenatal education to mothers of 12 weeks and above gestational age. "Concentrated" intrapartum counselling on correct breastfeeding practices, completion of infant vaccination, and use of contraception postpartum in addition to a hepatitis B test were offered to mothers in Todd 2010 study.

Incentives

Barham 2005 in Mexico combined conditional cash transfers with free provision of health and education services. The conditions for the cash transfer included receiving regular immunisation, growth monitoring, mother's attendance at health, hygiene, and nutrition education programmes; and nutritional supplements for children aged from birth to two years and for pregnant and lactating mothers.

In Nicaragua, one of the interventions in Maluccio 2004 was a monthly "food security" cash transfer ("bono alimentario" = USD 224 per year = 13% of the total amount of household expenditures in beneficiary households before the programme), conditional on attendance at monthly health educational workshops, on bringing their children aged under five for free scheduled preventive childcare appointments (which include the provision of anti‐parasite drugs, and vitamins and iron supplements), on having up‐to‐date vaccination, and on adequate weight gain. Morris 2004 assessed the effect of withdrawing monetary vouchers if the mothers were not up‐to‐date with routine antenatal care and well‐child preventive health care, and if the child did not attend school regularly.

Robertson 2013 in Zimbabwe compared two interventions. Both included a cash transfer of USD 18 per household and USD 4 per child every two months. In one of the arms, the transfer was on the condition that: those aged below 18 years with no birth certificate applied for one within three months; children aged under five years were up‐to‐date with immunisation, and attended growth monitoring clinics; children aged from six to 17 years had 90% monthly attendance at school; and a representative of every household attended two‐thirds of local parenting skills classes. In the second arm, there were no conditions attached to the cash transfer.

Patient reminder/recall

Seventeen studies implemented various types of reminder and recall interventions to promote the uptake of immunisation. Bangure 2015, Domek 2016, Domek 2019, Kawakatsu 2020, Kazi 2018, Linkins 1994, Oladepo 2021, and Uddin 2016 used messaging services (SMS, computer‐generated telephone messages) to remind caregivers of upcoming vaccination appointments. In some studies, the messages were sent up to three times prior to the appointment. Dissieka 2019 and Murthy 2019 sent voice messages, while Ekhaguere 2019 used a combination of automatically generated phone calls and text messaging. Nagar 2018 compared two reminder interventions, including the use of pendants only, and pendant plus voice call reminder. The sticker and culturally appropriate designed pendant (worn by the child) contained digital records of the child's vaccination history. The digital stickers and pendants were scanned by health workers when the children presented for vaccination.

Mobile software applications were developed (Ekhaguere 2019; Nagar 2018) or adapted (Uddin 2016) to register, input, track births and immunisation records of participants, and send out automated reminder messages.

Some studies combined recall/reminder interventions with other interventions. Usman 2009 and Usman 2011 delivered patient reminder and health education interventions. Usman 2009 and Usman 2011, conducted in urban and rural Pakistan respectively, redesigned and simplified immunisation cards to serve as reminders for immunisation appointments. The redesigned and enlarged cards displayed only the date of the next immunisation appointment on the exterior sides of the card. The date was printed in a large font size (42) for increased visibility when hung in the home. The other two intervention arms in the study received an educational intervention and a combination of redesigned cards and educational intervention respectively.

In Wallace 2019, the intervention sought to promote the ownership of home‐based records (HBR) or vaccination cards to remind caregivers of the vaccination services and schedule. Participants in one arm received HBRs only, while brightly coloured stickers containing the next vaccination appointment date were placed on the HBRs to serve as reminders for the next vaccination appointment in the second arm.

In Gibson 2017, one intervention arm received SMS reminders only, while the other two arms received SMS reminders and monetary incentives (75 KES or 200 KES). The combination of SMS and monetary incentives sought to test the hypothesis that money incentives may prod caregivers to access timely vaccination for their children.

Siddiqi 2020 compared tracking approaching using two reminder bracelets that conveyed different immunisation information. One arm received a bracelet that displayed comprehensive information on vaccination (schedule, antigen, and expected time of vaccination), while the second arm (Star bracelet) displayed only levels corresponding to the number of visits needed to complete the child's vaccination and attain a star level. Health workers perforated the bracelet at the points that corresponded to the vaccine(s) the child had received (group a) or the visit the child had made for vaccination (group b).

Digital tracking of children

In Chen 2016, village doctors actively tracked defaulting children using an EPI app. The app enabled them to schedule vaccination appointments, store vaccination records, educate caregivers, and track defaulters. A list containing the names of defaulting children, antigen(s) missed, and contact of the caregiver was sent to the village doctor on a daily basis via the EPI app. The functionality of the app allowed the doctor to place calls to the caregiver by clicking on the respective phone numbers on the list.

Provider‐oriented interventions

Interventions targeting providers in Georgia (Djibuti 2009) and Ethiopia (Amare 2021) included training in continuous supportive supervision, development of supportive supervision guidelines, and tools for immunisation district managers. In Nigeria, health workers were trained on interpersonal communication skills (Basheer 2021).

Health system interventions

Home visits

Brugha 1996 reported on the effects of home visits on childhood immunisation in Ghana: undergraduate students conducted the home visits, which aimed to identify non‐immunised children and refer them for immunisation at the health centre. Another systematic review considered these students to be lay/community health workers (Glenton 2011).

Immunisation outreach sessions

Three studies provided health camps (immunisation outreach sessions) to study communities (Banerjee 2010; Habib 2017; Sengupta 2017). In the Sengupta 2017 study, the camp was provided in collaboration with the community groups and leaders who provided the setting for the camps. Banerjee 2010 assessed the effects of regular monthly immunisation camps. This intervention focused on ensuring the regular availability of immunisation services. It consisted of a mobile immunisation team, including a nurse and assistant, who conducted monthly immunisation camps in villages. The camp was held on a fixed date and time every month in each village.

Habib 2017 assessed the effect of a health and polio immunisation campaign combined with community engagement. They set up fixed and mobile health camps that operated for four days to provide supplementary immunisation services. The camps were manned by trained staff who also assessed and catered to the basic health needs of mothers and children as they attended the immunisation camps. They engaged key stakeholder groups in the community including male, female, community elders, religious leaders, etc. in training sessions on general health promotion, health camps, and immunisation.

Integration of immunisation into other healthcare services

The Dicko 2011 study assessed the effects of integrating immunisation service delivery with intermittent preventive treatment of malaria in infants.

Health system funding

Two studies evaluated the impact of Payment‐for‐Performance (P4P) to health facilities based on the volume and quality of maternal and child health services provided, including child immunisation in Rwanda and Afghanistan respectively (Basinga 2011; Engineer 2016).

Community participation in the establishment of immunisation camps with community leaders

One study conducted in India engaged community leaders and set up active community groups for a vaccination outreach programme (Sengupta 2017). The outreach programme was delivered at locations provided by the community, which also identified adult guardians to stand in for absent parents so that children do not miss out on being immunised.

Multi‐faceted interventions

Recipient‐oriented plus recipient‐oriented interventions

Bangure 2015 combined routine health education with automated messages to mothers. One arm of the redesigned immunisation card intervention (HBR) combined the use of the card with facility‐based health education (Usman 2009; Usman 2011). Wallace 2019 combined a bright yellow sticker with a routinely used immunisation card.

Provider‐oriented plus recipient‐oriented

Oyo‐Ita 2021 had informal training of traditional and religious leaders on vaccination and health providers shared immunisation data with the community through the Ward Development Committee, in addition to the health workers being trained on the management of side effects of vaccination.

Health system plus recipient‐oriented interventions

Habib 2017 combined community mobilisation with health camps through individual and community group health education sessions involving men and women groups, community leaders, teachers, and other prominent members of the community to promote the services of the health camps offering maternal and child health immunisation services. One arm of the study by Banerjee and colleagues assessed a regular once‐monthly immunisation camp complemented with small material incentives in India (Banerjee 2010). The investigators offered parents 1 kg of raw lentils per immunisation administered and a set of "thalis" (metal plates used for meals) on completion of a child's full immunisation.

Health system plus provider‐oriented interventions

One arm of the Morris 2004 study set up quality assurance (QA) teams in rural Honduras in health centres allocated to the intervention. The team, with wide representation from the local communities, was trained on QA methods. They produced work plans that could include minor structural repairs to health centres and the purchase of equipment, materials, and essential drugs. This arm of the study also included training of lay nutrition promoters who conducted monthly weighing of children aged less than two years and counselling of mothers. This intervention was not carried out as stipulated in the protocol, as only 17% of the total budget for the intervention was disbursed.

QA training was limited to only the introduction to the QA course. It was not clear what the composition of the QA course was. However, QA usually aims to ensure that standards are met. This assures the service users of the quality of services and may encourage increased utilisation of services.

Comparison

The comparison groups received routine care in 21 studies (Andersson 2009; Bangure 2015; Banerjee 2010; Brugha 1996; Chen 2016; Dicko 2011; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Engineer 2016; Habib 2017; Kazi 2018; Morris 2004; Owais 2011; Oyo‐Ita 2021; Usman 2009; Usman 2011; Siddiqi 2020; Todd 2010; Wallace 2019). Only eight of these studies stated what comprised routine care (Bangure 2015; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Kazi 2018; Siddiqi 2020; Wallace 2019). In addition to the routine care, the comparison group in Chen 2016 and Todd 2010 received text message reminders and were tested for hepatitis b surface antigen respectively. Near Field Communication stickers (containing a child's digital immunisation record) were affixed on the existing child immunisation card in Nagar 2018. Oladepo 2021 provided an information leaflet on child nutrition and growth monitoring to the control arm. In the Robertson 2013 study, the comparison group received unconditional cash transfers, while Basinga 2011 provided funding to the comparison group through the traditional input funding.

Sixteen studies did not state what intervention was offered to the comparison group. It could, however, be assumed that they received routine care (Amare 2021; Barham 2005; Basheer 2021; Bolam 1998; Djibuti 2009; Gibson 2017; Hu 2017; Linkins 1994; Kawakatsu 2020; Maldonado 2020; Maluccio 2004; Murthy 2019; Pandey 2007; Powell‐Jackson 2018; Sengupta 2017; Uddin 2016).

Outcomes

Nineteen studies provided data on the proportion of the target population that was fully immunised by the recommended vaccine (Amare 2021; Andersson 2009; Banerjee 2010; Basheer 2021; Basinga 2011; Bolam 1998; Brugha 1996; Dicko 2011; Djibuti 2009; Habib 2017; Kawakatsu 2020; Maldonado 2020; Maluccio 2004; Owais 2011; Powell‐Jackson 2018; Robertson 2013; Usman 2009; Usman 2011; Wallace 2019). Other outcomes reported were: up‐to‐date with vaccination (Habib 2017; Oyo‐Ita 2021); DTP3/Penta 3 coverage (Amare 2021; Andersson 2009; Bolam 1998; Dicko 2011; Hu 2017; Oladepo 2021; Owais 2011; Oyo‐Ita 2021; Powell‐Jackson 2018; Sengupta 2017; Usman 2009; Usman 2011; Todd 2010); percentage change in immunisation coverage over time (Andersson 2009; Morris 2004); tetanus toxoid coverage in children (Pandey 2007); received at least one vaccine (Pandey 2007); oral polio coverage (Brugha 1996; Habib 2017); cost of the intervention (Andersson 2009); and coverage for tuberculosis and measles vaccines (Barham 2005).

All studies measured outcomes at the participant level, while six studies measured the outcome at the household level (Barham 2005; Maluccio 2004; Morris 2004; Pandey 2007; Robertson 2013; Sengupta 2017).

Follow‐up

The period of follow‐up varied between studies from three months to four years. Nine studies had no loss to follow‐up (Amare 2021; Bangure 2015; Basheer 2021; Dissieka 2019; Kawakatsu 2020; Linkins 1994; Siddiqi 2020; Usman 2009; Usman 2011), five studies had 2% to 5% loss to follow‐up (Morris 2004; Owais 2011; Pandey 2007; Powell‐Jackson 2018; Robertson 2013), and four studies had loss to follow‐up of 10% or more (Banerjee 2010; Basinga 2011; Bolam 1998; Todd 2010). In Murthy 2019, there was greater loss to follow‐up in the intervention arm compared to the control arm. Fifteen studies had two independent samples for pre‐ and post‐intervention surveys (Andersson 2009; Barham 2005; Basinga 2011; Brugha 1996; Chen 2016; Dicko 2011; Djibuti 2009; Habib 2017; Kazi 2018; Maluccio 2004; Morris 2004; Oyo‐Ita 2021; Robertson 2013; Uddin 2016; Sengupta 2017). Domek 2016, Ekhaguere 2019, Engineer 2016, Nagar 2018 and Wallace 2019 applied intention‐to‐treat analysis.

Excluded studies

We excluded 34 full‐text studies in this update. Together with the 54 excluded studies from the previous version, there are now 88 studies listed in the Characteristics of excluded studies table, with four studies awaiting classification.

Of the 12 studies that were awaiting assessment of their eligibility in Oyo‐Ita 2016, five are included in this review update (Bangure 2015; Basinga 2011; Domek 2016; Linkins 1994; Uddin 2016).

Risk of bias in included studies

Based on our predefined criteria, we assessed nine studies as having low risk of bias (Banerjee 2010; Dissieka 2019; Domek 2016; Domek 2019; Habib 2017; Owais 2011; Oyo‐Ita 2021; Pandey 2007; Powell‐Jackson 2018), nine studies as having unclear risk of bias (Bangure 2015; Basinga 2011; Chen 2016; Djibuti 2009; Ekhaguere 2019; Engineer 2016; Siddiqi 2020; Todd 2010; Uddin 2016), and the remaining 23 studies as having high risk of bias. Details of this assessment are presented in the risk of bias tables (Characteristics of included studies). We also summarise the risk bias assessment in Figure 1 (the risk of bias graph) and Figure 2 (the risk of bias summary). We reassessed the risk of bias in this version as 'risk of material bias' in line with Cochrane guidance.

Allocation

For random selection we assessed 32 studies as having low risk of bias, three studies had unclear risk of bias (Barham 2005; Brugha 1996; Kawakatsu 2020), and six studies had high risk of bias (Amare 2021; Basheer 2021; Linkins 1994; Murthy 2019; Oladepo 2021; Sengupta 2017) (Figure 1; Figure 2).

Blinding

Risk of bias in relation to blinding of participants, personnel, and outcome assessments was low for 19 studies (Amare 2021; Andersson 2009; Banerjee 2010; Basinga 2011; Bolam 1998; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Engineer 2016; Gibson 2017; Hu 2017; Kawakatsu 2020; Maldonado 2020; Owais 2011; Oyo‐Ita 2021; Pandey 2007; Powell‐Jackson 2018; Robertson 2013; Siddiqi 2020), unclear for 10 studies (Bangure 2015; Basheer 2021; Chen 2016; Djibuti 2009; Linkins 1994; Morris 2004; Oladepo 2021; Sengupta 2017; Todd 2010; Uddin 2016), and high for 12 studies (Barham 2005; Brugha 1996; Dicko 2011; Kazi 2018; Maluccio 2004; Murthy 2019; Nagar 2018; Robertson 2013; Siddiqi 2020; Usman 2009; Usman 2011; Wallace 2019).

Incomplete outcome data

The risk of attrition bias (completeness of outcome data) was low for 33 studies, unclear for two studies (Oladepo 2021; Todd 2010), and high for six studies (Bolam 1998; Gibson 2017; Hu 2017; Maldonado 2020; Maluccio 2004; Murthy 2019).

Selective reporting

Three studies had high risk of bias for selective reporting (Andersson 2009; Dicko 2011; Siddiqi 2020).

Other potential sources of bias

Fifteen studies had no other potential bias (Banerjee 2010; Bangure 2015; Basheer 2021; Bolam 1998; Chen 2016; Dicko 2011; Engineer 2016; Gibson 2017; Habib 2017; Maldonado 2020; Owais 2011; Oyo‐Ita 2021; Siddiqi 2020; Usman 2009; Usman 2011). The status of other potential bias was unclear for four studies (Barham 2005; Sengupta 2017; Todd 2010; Uddin 2016), and high for 22 studies (Amare 2021; Andersson 2009; Basinga 2011; Brugha 1996; Chen 2016; Dissieka 2019; Djibuti 2009; Domek 2016; Domek 2019; Ekhaguere 2019; Hu 2017; Kawakatsu 2020; Kazi 2018; Linkins 1994; Maluccio 2004; Morris 2004; Murthy 2019; Nagar 2018; Oladepo 2021; Pandey 2007; Powell‐Jackson 2018; Wallace 2019).

Effects of interventions

See: Table 1; Table 2; Table 3; Table 4; Table 5; Table 6; Table 7; Table 8; Table 9; Table 10; Table 11

We have included 11 summary of findings tables: Table 1; Table 2; Table 3; Table 4; Table 5; Table 6; Table 7; Table 8; Table 9; Table 10; Table 11.

Except for two outcomes (health education for measles vaccine and home‐based record for DTP3 vaccine uptake), there was no difference in the evidence reported in this version of the review and that in the last review. This was because most of the outcomes did not have additional studies; rather, this version has more interventions than the last version. Health education intervention for measles vaccine uptake had an additional three studies and home‐based records for DTP3 vaccine had an additional study. Though the magnitude of the evidence was smaller for these two outcomes in this review than in the last version, the evidence remains the same.

I. Recipient‐oriented interventions

These interventions included health education, the use of a combination of redesigned cards and health education, involvement of community leaders, and monetary incentives.

1. Health education compared to routine care

Included studies considered either community‐ or facility‐based health education.

1.1 Primary outcomes

• Reception ofDTP3/Penta 3 by one year of age

Seven studies reported on the effect of health education on DTP3 uptake (Andersson 2009; Hu 2017; Todd 2010; Owais 2011; Powell‐Jackson 2018; Usman 2009; Usman 2011). We pooled all except Todd 2010 in a meta‐analysis; Todd 2010 is presented as a narrative. Health education may slightly improve the proportion of children who take DTP3 (RR 1.36, 95% CI 1.15 to 1.62; I² = 89%; 6 studies, 4375 participants; low‐certainty evidence; Analysis 1.1; Table 1). The data showed substantial heterogeneity. Subgroup analysis by facility‐ or community‐based health education was explored and the results are as shown below.

1.1. Analysis.

Comparison 1: Health education, Outcome 1: Reception of DTP3 by 1 year of age

Facility‐based health education may make little or no impact on the uptake of DTP3 (RR 1.21, 95% CI 1.01 to 1.46; I² = 86%; 3 studies, 2355 participants; Analysis 1.1) (Hu 2017; Usman 2009; Usman 2011).

Community‐based health education probably improved coverage of DTP3 (RR 1.55, 95% CI 1.27 to 1.88; I² = 46%; 3 studies, 2020 participants; Analysis 1.1) (Andersson 2009; Owais 2011; Powell‐Jackson 2018).

There were no important differences between the subgroups of facility‐based health education and community‐based health education in comparison to routine care for DTP3. The subgroup analysis showed the treatment effect favouring both types of health education (facility‐based RR 1.21, 95% CI 1.01 to 1.46; community‐based RR 1.55, 95% CI 1.27 to 1.88). Statistical heterogeneity was still present within each of the subgroups. Hence, it is uncertain whether the type of health education modifies the treatment effect.

The Todd 2010 study reported no difference in DTP3 uptake between the study arms by 10 months (OR 1.02, 95% CI 0.75 to 1.39).

• All recommended vaccines by two years of age

None of the included studies on health education reported this outcome.

1.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: health education probably makes little or no difference to the proportion of children who receive BCG (RR 0.99, 95% CI 0.96 to 1.01; 2 studies, 1557 participants; moderate‐certainty evidence; Analysis 1.2; Table 1) (Hu 2017; Powell‐Jackson 2018).

1.2. Analysis.

Comparison 1: Health education, Outcome 2: Uptake of BCG vaccine

OPV3 uptake: the intervention may lead to a slight increase in the proportion of children with OPV3 uptake (RR 1.08, 95% CI 1.04 to 1.11; 1 study, 851 participants; low‐certainty evidence; Analysis 1.3; Table 1) (Hu 2017).

1.3. Analysis.

Comparison 1: Health education, Outcome 3: Uptake of OPV3 vaccine

HBV3 uptake: health education may slightly improve HBV3 uptake (RR 1.07, 95% CI 1.03 to 1.10; 1 study, 851 participants; low‐certainty evidence; Analysis 1.4; Table 1) (Hu 2017).

1.4. Analysis.

Comparison 1: Health education, Outcome 4: Uptake of HBV3 vaccine

BCG + DTP3 + OPV uptake: the intervention probably makes little or no difference to the uptake of BCG + DTP3 + OPV vaccines at three months of age (RR 1.02, 95% CI 0.95 to 1.11; 1 study, 190 participants; moderate‐certainty evidence; Analysis 1.5) (Bolam 1998).

1.5. Analysis.

Comparison 1: Health education, Outcome 5: Uptake of BCG + DTP3 + OPV vaccines

Measles uptake: health education may improve the proportion of children with measles vaccine uptake (RR 1.25, 95% CI 1.06 to 1.47; I² = 91%; 4 studies, 3343 participants; low‐certainty evidence; Analysis 1.6; Table 1) (Andersson 2009; Hu 2017; Maldonado 2020; Powell‐Jackson 2018). The pooled data showed substantial heterogeneity, which could not be explained by subgroup analysis of facility‐ or community‐based health education.

1.6. Analysis.

Comparison 1: Health education, Outcome 6: Uptake of measles vaccine

There were no important differences between the subgroups of facility‐based health education and community‐based health education in comparison to routine care for measles. The subgroup effect favoured both types of health education (facility‐based RR 1.04, 95% CI 1.02 to 1.07; community‐based RR 1.38, 95% CI 1.12 to 1.70), but with a greater treatment effect in the community‐based health education subgroup. Statistical heterogeneity was present and only one study contributed to the facility‐based health education subgroup.

We found that information campaigns (presentation of audiotape messages, and distribution of posters and leaflets in the community) probably increase the coverage of at least one dose of a vaccine (RR 1.58, 95% CI 1.21 to 2.05; 1 study, 228 participants; moderate‐certainty evidence; Analysis 1.7) (Pandey 2007).

1.7. Analysis.

Comparison 1: Health education, Outcome 7: Uptake of at least 1 vaccine

• Under five years of age fully immunised with all scheduled vaccines

Health education may make little or no difference in improving the proportion of children under the age of five years fully immunised with all scheduled vaccines (RR 1.24, 95% CI 1.06 to 1.44; I² = 85%; 3 studies, 2387 participants; low‐certainty evidence; Analysis 1.8) (Hu 2017; Maldonado 2020; Powell‐Jackson 2018).

1.8. Analysis.

Comparison 1: Health education, Outcome 8: Reception of all recommended vaccines by 2 years of age

• Cost of intervention

Evaluation by Andersson 2009 indicates that community‐based health education costs USD 9 per child. In Powell‐Jackson 2018, the cost per additional child with DTP3 was estimated at USD 165, and measles at USD 109. It also reported USD 186 for disability‐adjusted life years (DALY) averted, and under‐five death averted was reported as USD 5572.65.

None of the included studies on health education reported on other secondary outcomes: occurrence of vaccine‐preventable diseases, attitude of caregivers, and adverse events of the intervention.

2. Monetary incentives or disincentives compared to routine care

2.1 Primary outcomes

None of the included studies on household dis/incentives reported on DTP3 uptake or uptake of all recommended vaccines by two years of age.

2.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: we are uncertain if monetary incentives have an effect on uptake of BCG vaccination (RR 1.00, 95% CI 0.99 to 1.01; 1 study, 2175 participants; very low‐certainty evidence; Analysis 2.1; Table 2) (Barham 2005).

2.1. Analysis.

Comparison 2: Monetary incentive, Outcome 1: Uptake of BCG vaccine

Measles uptake: we are also uncertain if monetary incentives have an effect on measles vaccination uptake (RR 1.06, 95% CI 0.93 to 1.21; 2 studies, 2709 participants; very low‐certainty evidence; Analysis 2.2.1; Table 2) (Barham 2005; Morris 2004).

2.2. Analysis.

Comparison 2: Monetary incentive, Outcome 2: Uptake of measles/MMR vaccine

MMR uptake: similarly, we are uncertain if service‐level monetary incentives have an effect on coverage of MMR (RR 1.06, 95% CI 0.95 to 1.18; 1 study, 615 participants; very low‐certainty evidence; Analysis 2.2.2; Table 2), and a combination of household and service level incentives has little or no effect on measles uptake (RR 1.09, 95% CI 0.96 to 1.24; 1 study, 456 participants; very low‐certainty evidence; Analysis 2.2.3; Table 2) (Morris 2004).

• Under five years of age fully immunised with all scheduled vaccines

Household monetary incentives may improve coverage of all vaccines among children aged under five years (RR 1.05, 95% CI 0.92 to 1.20; 2 studies, 1000 participants; low‐certainty evidence; Analysis 2.3; Table 2) (Maluccio 2004; Robertson 2013).

2.3. Analysis.

Comparison 2: Monetary incentive, Outcome 3: Under 5 years of age fully immunised with all scheduled vaccine

None of the included studies on household dis/incentives reported on the occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, and adverse events of the intervention.

Patient‐reminder interventions

Thirteen studies reported different patient reminder interventions for DTP3 uptake (Bangure 2015; Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019; Gibson 2017; Kazi 2018; Linkins 1994; Nagar 2018; Siddiqi 2020; Usman 2009; Usman 2011; Oladepo 2021). These included home‐based records (HBR) (immunisation cards), sticker on HBR, SMS/phone calls, and wearable reminders.

3. Home‐based records only compared to routine care

3.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Home‐based records ('reminder‐type' vaccination cards) may improve DTP3 coverage (RR 1.36, 95% CI 1.06 to 1.75; I² = 80%; 3 studies, 4019 participants; low‐certainty evidence; Analysis 3.1.1; Table 3) (Usman 2009; Usman 2011; Wallace 2019).

3.1. Analysis.

Comparison 3: Home‐based record, Outcome 1: Uptake of DTP3 vaccine

None of the included studies reported on uptake of all recommended vaccines by two years of age.

3.2 Secondary outcomes

None of the included studies on home‐based records only reported on under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

4. Digital registers compared with routine care

4.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Digital registers probably have no effect in increasing the proportion of children who received DTP3/Penta 3 by one year of age (RR 0.98, 95% CI 0.89 to 1.09; 2 studies, 328 participants; moderate‐certainty evidence; Analysis 4.1; Table 4) (Chen 2016; Nagar 2018). However, the 95% CI includes both benefit and harm.

4.1. Analysis.

Comparison 4: Digital register, Outcome 1: Uptake of DTP3 vaccine

• Uptake of all recommended vaccines by two years of age

The intervention may have little or no effect in improving the proportion of children fully immunised by two years of age (RR. 1.03, 95% CI 0.88 to 1.20; 1 study, 205 participants; low‐certainty evidence; Analysis 4.2; Table 4) (Chen 2016).

4.2. Analysis.

Comparison 4: Digital register, Outcome 2: Reception of all recommended vaccines by 2 years of age

4.2 Secondary outcomes

• Uptake of other vaccines under study

Use of digital registers to track unvaccinated/partially vaccinated children (1 study, 205 participants; Chen 2016) may have little or no effect on BCG uptake (RR 0.98, 95% CI 0.92 to 1.04; low‐certainty evidence; Analysis 4.3), OPV3 uptake (RR 1.06, 95% CI 0.97 to 1.17; Analysis 4.4), HBV3 uptake (RR 0.98, 95% CI 0.89 to 1.08; low‐certainty evidence; Analysis 4.5; Table 4), or measles vaccine uptake (RR 1.06, 95% CI 0.97 to 1.17; low‐certainty evidence; Analysis 4.6).

4.3. Analysis.

Comparison 4: Digital register, Outcome 3: Uptake of BCG vaccine

4.4. Analysis.

Comparison 4: Digital register, Outcome 4: Uptake of OPV3 vaccine

4.5. Analysis.

Comparison 4: Digital register, Outcome 5: Uptake of HBV3 vaccine

4.6. Analysis.

Comparison 4: Digital register, Outcome 6: Uptake of measles vaccine

None of the included studies on digital registers reported on under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

5. Phone calls/SMS compared with routine care

5.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

The use of phone calls/SMS may slightly improve DPT3/Penta 3 uptake compared to routine immunisation care (RR 1.12, 95% CI 1.00 to 1.25; I² = 92%; 6 studies, 3869 participants; low‐certainty evidence; Analysis 5.1; Table 5) (Bangure 2015; Dissieka 2019; Domek 2016; Ekhaguere 2019; Gibson 2017; Kazi 2018). There was substantial heterogeneity, which we explored by subgroup analysis based on study setting.

5.1. Analysis.

Comparison 5: Phone call/SMS, Outcome 1: Reception of DTP3/Penta 3 by 2 years of age

There were no important differences between the subgroups of urban, rural, and combined urban and rural settings for phone call/SMS interventions in comparison to routine care for DTP3/Penta 3. The subgroup effect showed the effect favouring the treatment in all settings (urban RR 1.16, 95% CI 0.99 to 1.35; rural RR 0.99, 95% CI 0.96 to 1.03; urban + rural RR 1.27, 95% CI 1.19 to 1.37). However, only the combined setting subgroup found a significant effect. Statistical heterogeneity was present and only one study contributed to the combined setting subgroup.

Two non‐randomised controlled studies were excluded from the meta‐analysis (Linkins 1994; Oladepo 2021). The two studies showed that SMS may have little or no effect in improving Penta 3 uptake (RR 1.00, 95% CI 0.87 to 1.16; 1 study, 1145 participants; Linkins 1994) (RR 1.20, 95% CI 0.97 to 1.50; 1 study, 2349 participants; Oladepo 2021).

• Uptake of all recommended vaccines by two years of age

Phone calls/SMS may make little or no difference in improving the proportion of children that receive full vaccination by two years of age (RR 1.06, 95% CI 0.99 to 1.12; 5 studies, 10,414 participants; low‐certainty evidence; Analysis 5.3; Table 5) (Domek 2016; Domek 2019; Gibson 2017; Kawakatsu 2020; Uddin 2016). It is uncertain if voice messages improve full vaccination of children by two years of age (OR 1.53, 95% CI 1.14 to 2.05; very low‐certainty evidence) (Murthy 2019, a non‐RCT).

5.3. Analysis.

Comparison 5: Phone call/SMS, Outcome 3: Reception of all recommended vaccines by 2 years of age

5.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: the outcome was reported by two studies that could not be pooled because one was an RCT (Gibson 2017) and the other a non‐RCT (Oladepo 2021). Phone calls/SMS may not improve BCG uptake (RR 0.98, 95% CI 0.82 to 1.18; 1 study, 748 participants; low‐certainty evidence; Analysis 5.4; Table 5) (Gibson 2017). We are uncertain of the improved uptake reported by Oladepo 2021 (RR 1.89, 95% CI 1.31 to 2.74; 1 study, 2337 participants; very low‐certainty evidence).

5.4. Analysis.

Comparison 5: Phone call/SMS, Outcome 4: Uptake of BCG vaccine

OPV3 uptake: the intervention probably does not improve OPV3 vaccine uptake (RR 0.99, 95% CI 0.94 to 1.05; 2 studies, 1069 participants; moderate‐certainty evidence; Analysis 5.5.1; Table 5) (Domek 2016; Gibson 2017). However, results from a non‐RCT excluded from the meta‐analysis were not congruent with those from the RCTs and rather suggested that the intervention may improve uptake of OPV3 (RR 1.13, 95% CI 1.08 to 1.17; 1 study, 2337 participants) (Oladepo 2021).

5.5. Analysis.

Comparison 5: Phone call/SMS, Outcome 5: Uptake of OPV3 vaccine

Measles vaccine uptake: the pooled data from three studies that contributed to the outcome on measles vaccine uptake was highly heterogeneous (I² = 95%); the report is, therefore, presented as a narrative. The three studies reported that the intervention may have little or no effect on measles vaccine uptake (RR 1.60, 95% CI 1.44 to 1.78; 1 study, 1596 participants; Dissieka 2019); (RR 1.12, 95% CI 1.01 to 1.25; 1 study, 600 participants; Ekhaguere 2019); (RR 1.04, 95% CI 0.97 to 1.11; 1 study, 766 participants; Gibson 2017).

Yellow fever vaccine: we are uncertain whether phone calls/SMS may improve yellow fever vaccination (RR 3.17, 95% CI 2.21 to 4.55; 1 study, 734 participants) (Oladepo 2021, a non‐RCT).

• Under five years of age fully vaccinated with all scheduled vaccines

Phone calls/SMS may have little or no effect on uptake of full vaccination for children under five years of age (RR 1.06, 95% CI 0.09 to 1.13; I² = 76%; 5 studies, 10,414 participants; low‐certainty evidence; Analysis 5.3.1; Table 5) (Domek 2016; Domek 2019; Gibson 2017; Kawakatsu 2020; Uddin 2016).

• Cost of intervention

Bangure 2015 provided estimates of the cost of sending SMS reminders (three messages before the appointment day) for the entire immunisation schedule of one child up to 18 months of age to be USD 0.99. Ekhaguere 2019 estimated a cost of USD 0.0075 to send an SMS and USD 0.015 for an automated call per minute.

None of the included studies on phone call/SMS reported on the occurrence of vaccine‐preventable diseases, attitude of caregivers, or adverse events of the intervention.

6. Wearable reminders compared with routine care

6.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Wearable reminders probably do not increase the uptake of DTP3 (RR 1.02, 95% CI 0.97 to 1.07; 2 studies, 1567 participants; moderate‐certainty evidence; Analysis 6.1; Table 6) (Nagar 2018; Siddiqi 2020), but the 95% CI includes both benefit and harm.

6.1. Analysis.

Comparison 6: Wearable reminder, Outcome 1: Reception of DTP3/Penta 3 vaccine by 2 years of age

• Uptake of all recommended vaccines by two years of age

None of the included studies on wearable reminders reported this outcome.

6.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: wearable reminders may have little or no effect in improving uptake of BCG vaccine (RR 0.84, 95% CI 0.74 to 0.94; 1 study, 1382 participants; low‐certainty evidence; Analysis 6.2; Table 6) (Siddiqi 2020) and measles vaccine uptake (RR 1.04, 95% C1 0.97 to 1.12; 1 study, 1440 participants; low‐certainty evidence; Analysis 6.3; Table 6) (Siddiqi 2020), but the 95% CI includes both benefit and harm.

6.2. Analysis.

Comparison 6: Wearable reminder, Outcome 2: Uptake of BCG vaccine

6.3. Analysis.

Comparison 6: Wearable reminder, Outcome 3: Uptake of measles vaccine

None of the included studies on wearable reminders reported on the proportion of children under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

II. Provider‐oriented interventions

7. Training on supportive supervision compared with routine care

7.1 Primary outcomes

• Reception ofDTP3/Penta 3 by one year of age

Two non‐randomised controlled studies assessed the impact of training health workers to provide supportive supervision for health providers on immunisation coverage and are reported as a narrative (Amare 2021; Djibuti 2009). There are differing reports from the two studies. The difference in the uptake of DTP3‐containing vaccine between the intervention and control groups was 17.40% (95% CI 2.04 to 32.79; P = 0.027; low‐certainty evidence) in Amare 2021, and 4.30% (P = 0.285; low‐certainty evidence) in Djibuti 2009.

• Uptake of all recommended vaccines by two years of age

Two non‐randomised studies assessed supportive supervision (Amare 2021) and interpersonal communication (Basheer 2021); the results are presented as a narrative. We are uncertain whether training of health workers on interpersonal communication increases full vaccination (RR 5.65, 95% CI 3.62 to 8.83; 1 study, 420 participants; very low‐certainty evidence; Analysis 7.1) (Basheer 2021). We are also uncertain if supportive supervision improves full vaccination by two years of age (difference in difference 6.6, 95% CI 1.33 to 31.90; P = 0.034; very low‐certainty evidence) (Amare 2021).

7.1. Analysis.

Comparison 7: Training of health providers ‐ IPC, Outcome 1: Uptake of all recommended vaccines by 2 years of age

7.2 Secondary outcomes

• Uptake of other vaccines under study

OPV3 uptake: supportive supervision of health providers may have little or no effect on the uptake of OPV3 vaccine. The difference in coverage between the intervention and control groups was 8.40% (P = 0.173).

HPV3 uptake: supportive supervision may also have little to no effect on HPV3 vaccine uptake. The difference in coverage between the intervention and control groups was 13.40% (P = 0.172) for HBV3 (low‐certainty evidence) (Djibuti 2009).

None of the included studies on supportive supervision reported on under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

III. Health system interventions

8. Home visit compared with routine care

8.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

The included study on home visits did not report on the uptake of DTP3‐containing vaccine.

• Uptake of all recommended vaccines by two years of age

We are uncertain if home visits improve the proportion of children under two years of age that receive full vaccination (RR 1.29, 95% CI 1.15 to 1.45; 1 study, 419 participants; very low‐certainty evidence; Analysis 8.1; Table 8) (Brugha 1996).

8.1. Analysis.

Comparison 8: Home visit, Outcome 1: Uptake of all recommended vaccines by 2 years of age

8.2 Secondary outcomes

• Uptake of other vaccines under study

OPV3 uptake: we are uncertain whether home visits improve OPV3 (RR 1.22, 95% CI 1.10 to 1.35; 1 study, 419 participants; very low‐certainty evidence; Analysis 8.2; Table 8) (Brugha 1996).

8.2. Analysis.

Comparison 8: Home visit, Outcome 2: Uptake of OPV3 vaccine

Measles uptake: we are also uncertain if home visits improve measles vaccine coverage (RR 1.26, 95% CI 1.14 to 1.39; 1 study, 419 participants; very low‐certainty evidence; Analysis 8.3; Table 8) (Brugha 1996).

8.3. Analysis.

Comparison 8: Home visit, Outcome 3: Uptake of measles vaccine

None of the included studies reported on other secondary outcomes: under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

9. Immunisation outreach compared with routine care

9.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

We are uncertain whether immunisation outreach improves DTP3‐containing vaccine coverage compared to routine care (RR 1.32, 95% CI 1.11 to 1.56; 1 study, 541 participants; very low‐certainty evidence; Analysis 9.1; Table 9) (Sengupta 2017).

9.1. Analysis.

Comparison 9: Immunisation outreach, Outcome 1: Reception of DTP3 by 1 year of age

• Uptake of all recommended vaccines by two years of age

We are also uncertain whether immunisation outreach increases the proportion of children who receive all vaccines by two years of age (RR 1.33, 95% CI 1.00 to 1.76; 1 study, 309 participants; very low‐certainty evidence; Analysis 9.2) (Sengupta 2017).

9.2. Analysis.

Comparison 9: Immunisation outreach, Outcome 2: Uptake of all recommended vaccines by 2 years of age

9.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: we are uncertain whether regular immunisation outreach improves or reduces uptake of BCG vaccination (RR 1.06, 95% CI 0.99 to 1.13; 1 study, 647 participants; very low‐certainty evidence; Analysis 9.3; Table 9) (Sengupta 2017).

9.3. Analysis.

Comparison 9: Immunisation outreach, Outcome 3: Uptake of BCG vaccine

HBV3 uptake: we are uncertain if regular immunisation outreach improves HBV3 uptake (RR 1.36, 95% CI 1.13 to 1.64; 1 study, 541 participants; very low‐certainty evidence; Analysis 9.4; Table 9) (Sengupta 2017).

9.4. Analysis.

Comparison 9: Immunisation outreach, Outcome 4: Uptake of HBV3 vaccine

OPV3 uptake: we are uncertain if regular immunisation outreach improves OPV3 uptake (RR 1.38, 95% CI 1.16 to 1.65; 1 study, 541 participants; very low‐certainty evidence; Analysis 9.5; Table 9) (Sengupta 2017).

9.5. Analysis.

Comparison 9: Immunisation outreach, Outcome 5: Uptake of OPV3 vaccine

Measles uptake: we are uncertain if regular immunisation outreach improves measles uptake (RR 1.26, 95% CI 0.91 to 1.74; 1 study, 647 participants; very low‐certainty evidence; Analysis 9.6; Table 9) (Sengupta 2017).

9.6. Analysis.

Comparison 9: Immunisation outreach, Outcome 6: Uptake of measles vaccine

• Under five years of age fully immunised with all scheduled vaccines

Immunisation outreach probably improves full vaccination of children under five years of age (RR 3.09, 95% CI 2.11 to 4.53; 1 study, 1239 participants; moderate‐certainty evidence; Analysis 9.7.2; Table 9) (Banerjee 2010).

9.7. Analysis.

Comparison 9: Immunisation outreach, Outcome 7: Under 5 years of age fully immunised with all scheduled vaccines

• Cost of intervention

The average cost for fully immunising a child was estimated at USD 27.94 for outreach plus incentive and USD 55.83 for the immunisation camp without incentive (Banerjee 2010).

The included studies did not report on other secondary outcomes: occurrence of vaccine‐preventable diseases, attitude of caregivers, or adverse events of the intervention.

10. Integration of immunisation with other healthcare services compared with routine care

10.1 Primary outcomes

• Reception of DTP3 by one year of age

Integrating immunisation services with intermittent prophylactic treatment of malaria in infants may improve DTP3‐containing vaccine coverage (RR 1.27, 95% CI 1.17 to 1.38; 1 study, 2192 participants; low‐certainty evidence; Analysis 10.1; Table 10) (Dicko 2011).

10.1. Analysis.

Comparison 10: Integration of immunisation with other health services, Outcome 1: Reception of DTP3/Penta 3 by 1 year of age

• Uptake of all recommended vaccines by two years of age

Integration of immunisation services with prophylactic treatment of malaria in infants may improve full vaccination among children under the age of two years (RR 1.29, 95% CI 1.16 to 1.44; 1 study, 1700 participants; low‐certainty evidence; Analysis 10.2; Table 10) (Dicko 2011).

10.2. Analysis.

Comparison 10: Integration of immunisation with other health services, Outcome 2: Uptake of all recommended vaccines by 2 years of age

10.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: integrating immunisation services with intermittent prophylactic treatment of malaria in infants may have no effect on BCG coverage (RR 0.97, 95% CI 0.93 to 1.01; 1 study, 2089 participants; low‐certainty evidence; Analysis 10.3; Table 10) (Dicko 2011).

10.3. Analysis.

Comparison 10: Integration of immunisation with other health services, Outcome 3: Uptake of BCG vaccine

Measles uptake: integrating immunisation services with intermittent prophylactic treatment of malaria in infants may have no effect on measles vaccine uptake (RR 1.13, 95% CI 1.04 to 1.22; 1 study, 1370 participants; low‐certainty evidence; Analysis 10.4; Table 10) (Dicko 2011).

10.4. Analysis.

Comparison 10: Integration of immunisation with other health services, Outcome 4: Uptake of measles vaccine

Yellow fever uptake: integrating immunisation services with intermittent prophylactic treatment of malaria in infants may have no effect on yellow fever vaccine uptake (RR 1.13, 95% CI 1.04 to 1.22; 1 study, 1383 participants; low‐certainty evidence; Analysis 10.5; Table 10) (Dicko 2011).

10.5. Analysis.

Comparison 10: Integration of immunisation with other health services, Outcome 5: Uptake of yellow fever vaccine

The included study did not report on other secondary outcomes: under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

11. Funding of the health system (pay for performance) compared with routine care

Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Engineer 2016 reported no difference in the percentage of children that received Penta 3 immunisation following pay for performance (P4P) funding of the health system. The mean percentage of children vaccinated in the intervention arm was 49.60% (95% CI 43.50 to 55.60) versus control 52.30% (95% CI 46 to 58; P = 0.4; very low‐certainty evidence).

• Uptake of all recommended vaccines by two years of age

None of the included studies reported on this outcome.

Secondary outcomes

• Under five years of age fully immunised with all scheduled vaccines

Basinga 2011 evaluated the effect of payment for performance (P4P) against the traditional input financing. Data were not available to be extracted. The study provided low‐certainty evidence that P4P may have little or no effect on improving full vaccination (β = ‐0.055, 95% CI ‐0.184 to 0.074; P = 0.390).

None of the included studies reported on the other secondary outcomes: uptake of other vaccines under study, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

IV. Multi‐faceted interventions

Provider‐oriented plus recipient‐oriented interventions

12. Engagement of community leaders compared with routine care

12.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Engagement of community leaders in combination with a provider intervention probably increases the uptake of DTP3/Penta 3 vaccine (RR 1.37, 95% CI 1.11 to 1.69; 1 study, 2020 participants; moderate‐certainty evidence; Analysis 11.1; Table 11) (Oyo‐Ita 2021).

11.1. Analysis.

Comparison 11: Engagement of community leaders, Outcome 1: Reception of DTP3/Penta 3 vaccine by 1 year of age

• Uptake of all recommended vaccines by two years of age

The included study did not report on this outcome.

12.2 Secondary outcomes

• Uptake of other vaccines under study

Measles uptake: a combination of community leader engagement and a provider intervention probably improves measles vaccine uptake (RR 1.96, 95% CI 1.61 to 2.39; 1 study, 1227 participants; moderate‐certainty evidence; Analysis 11.2; Table 11) (Oyo‐Ita 2021).

11.2. Analysis.

Comparison 11: Engagement of community leaders, Outcome 2: Uptake of measles vaccine

The included study did not report on other secondary outcomes: under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

Combination of two recipient‐oriented interventions

13. Home‐based records plus health education compared with routine care

13.1 Primary outcomes

• Reception ofDTP3/Penta 3 by one year of age

Home‐based records in combination with facility‐based health education may increase the uptake of DTP3‐containing vaccine by children under the age of one year (RR 1.49, 95% CI 1.22 to 1.82; I² = 79%; 2 studies, 1502 participants; low‐certainty evidence; Analysis 3.1.2; Table 3) (Usman 2009; Usman 2011). The pooled data showed substantial heterogeneity, which could not be explored due to the small number of included studies.

• Uptake of all scheduled vaccines by two years of age

None of the included studies reported this outcome.

13.2 Secondary outcomes

None of the included studies reported on the other secondary outcomes: under five years of age fully immunised with all scheduled vaccines, uptake of other vaccines under study, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

14. Home‐based records plus sticker compared with routine care

14.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

Home‐based records plus sticker may increase DTP3 uptake when compared with routine care (RR 1.46, 95% CI 1.02 to 2.09; 1 study, 2182 participants; low‐certainty evidence; Analysis 3.1.3; Table 3) (Wallace 2019).

• Uptake of all recommended vaccines by two years of age

The included study did not report on this outcome.

14.2 Secondary outcomes

The included study did not report on the secondary outcomes: uptake of other vaccines under study, under five years of age fully immunised with all scheduled vaccines, the occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

15. Phone calls/SMS plus monetary incentive compared with routine care

15.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

A combination of phone calls/SMS with monetary incentives may have little or no effect on the uptake of DTP3/Penta 3 vaccine (RR 1.01, 95% CI 1.00 to 1.03; 1 study, 766 participants; low‐certainty evidence; Analysis 5.2; Table 5) (Gibson 2017).

5.2. Analysis.

Comparison 5: Phone call/SMS, Outcome 2: Uptake of DTP3 (SMS + monetary incentive intervention)

• Uptake of all recommended vaccines by two years of age

A combination of phone calls/SMS with monetary incentives may have a slight impact in increasing the proportion of children under two years of age that receive all scheduled vaccines (RR 1.09, 95% CI 1.02 to 1.16; 1 study, 766 participants; low‐certainty evidence; Analysis 5.3; Table 5) (Gibson 2017).

15.2 Secondary outcomes

• Uptake of other vaccines under study

BCG uptake: phone calls plus monetary incentives may have little or no effect on the uptake of BCG (RR 1.00, 95% CI 0.84 to 1.20; 1 study, 766 participants; low‐certainty evidence; Analysis 5.4.2; Table 5) (Gibson 2017).

OPV3 uptake: phone calls plus monetary incentives may have little or no effect on the uptake of OPV3 (RR 1.01, 95% CI 0.99 to 1.04; 1 study, 766 participants; low‐certainty evidence; Analysis 5.5.2; Table 5) (Gibson 2017).

Measles: phone calls plus monetary incentives may have little or no effect on measles vaccine uptake (RR 1.07, 95% CI 1.01 to 1.14; 1 study, 766 participants; low‐certainty evidence; Analysis 5.6 2; Table 5) (Gibson 2017).

5.6. Analysis.

Comparison 5: Phone call/SMS, Outcome 6: Uptake of measles vaccine

Health system‐oriented plus provider‐oriented interventions

16. Logistic support to health facilities plus training healthcare providers

16.1 Primary outcomes

The included study did not report on the primary outcomes: DTP3/Penta 3, uptake of all recommended vaccines by two years of age.

16.2 Secondary outcomes

• Uptake of other vaccines under study

MMR uptake: one arm of the study Morris 2004 aimed to strengthen peripheral health services through training Quality Assurance (QA) teams (provider package) and the provision of equipment, drugs, and materials (health system package), and also provided nutritional promotion. This arm of the intervention was not delivered as per protocol. We are uncertain if this intervention improves or reduces MMR coverage (RR 1.06, 95% CI 0.95 to 1.18 ; 1 study, 615 participants; very low‐certainty evidence; Analysis 2.2.2; Table 2).

The included study did not report on the other secondary outcomes: under five years of age fully immunised with all scheduled vaccines, occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

Health system‐oriented plus recipient‐oriented intervention

17. Logistic support to health facilities plus household monetary incentives compared with routine care

17.1 Primary outcomes

• Reception of DTP3/Penta 3 by one year of age

The included study did not report on this outcome.

• Uptake of all recommended vaccines by two years of age

The included study for this intervention did not report this outcome.

17.2 Secondary outcomes

Measles uptake: we are uncertain if the intervention combining logistic support to health facilities and monetary incentives to household increases the uptake of measles vaccine (RR 1.09, 95% CI 0.96 to 1.24; 1 study, 456 participants; very low‐certainty evidence; Analysis 2.2.3; Table 2) (Morris 2004).

18. Immunisation outreach plus community health education compared with routine care

18.1 Primary outcomes

The included study did not report on the primary outcomes: DTP3/Penta 3 and uptake of all recommended vaccines by two years of age.

18.2 Secondary outcomes

• Uptake of other vaccines under study

The included study for this intervention did not report this outcome.

• Under five years of age fully immunised with all scheduled vaccines

Immunisation outreach plus community health education probably increases the proportion of fully immunised under five‐year‐olds (RR 1.28, 95% CI 1.23 to 1.33; 1 study, 49,444 participants; moderate‐certainty evidence; Analysis 9.7.2; Table 9) (Habib 2017).

19. Immunisation outreach plus non‐monetary incentives compared with routine care

19.1 Primary outcomes

• Reception ofDTP3/Penta 3 by one year of age

The included study did not report on this outcome.

• Uptake of all recommended vaccines by two years of age

The included study for this intervention did not report this outcome.

19.2 Secondary outcomes

A combination of immunisation outreach and non‐monetary incentives probably increases the uptake of full vaccination by under fives (RR 6.66, 95% CI 4.78 to 9.28; 1 study, 1242 participants; moderate‐certainty evidence; Analysis 9.7.3) (Banerjee 2010).

The included study did not report on the other secondary outcomes: occurrence of vaccine‐preventable diseases, costs of the intervention, attitude of caregivers, or adverse events of the intervention.

Discussion

In this review we set out to identify which intervention models are associated with improved immunisation coverage. We categorised the interventions as recipient‐oriented, provider‐oriented, health system, multi‐faceted (any combination of the above categories of interventions), and others. The primary outcomes of interest were the proportion of children who received DTP3/Penta 3 by one year of age, and the proportion of children who received all recommended vaccines by two years of age. The scope of the review was limited to LMICs and included a wide range of possible study designs and interventions. Participants were children under five years of age, caregivers of children, healthcare workers administering vaccines, and health systems supporting immunisation.

Summary of main results

Forty‐one studies from four upper‐middle‐income countries, 11 lower‐middle‐income countries, and three lower‐income countries met the inclusion criteria. The countries include Afghanistan, China, Côte d'Ivoire, Ethiopia, Georgia, Ghana, Guatemala, Honduras, India, Indonesia, Kenya, Mali, Mexico, Nepal, Nicaragua, Nigeria, Pakistan, Rwanda, and Zimbabwe. The settings for the studies varied from urban, urban slum, rural, to high‐risk populations. Twenty studies were cluster‐randomised and 15 studies were individually randomised controlled trials. Six studies were quasi‐randomised studies. The interventions evaluated in the studies were implemented either as single interventions or as multi‐faceted interventions.

Recipient‐oriented interventions had varying effects on the outcomes studied. Health education may slightly improve the uptake of DTP3 (low‐certainty evidence). It may improve the uptake of measles vaccine (low‐certainty evidence) and probably improves the uptake of at least one vaccine (moderate‐certainty evidence), but has little or no effect on BCG uptake (low‐certainty evidence). Patient reminders (home‐based record only or in combination with health education and phone calls/SMS) may improve DTP3 uptake (low‐certainty evidence). Other patient reminder interventions: home‐based records plus sticker (low‐certainty evidence), wearable reminders (moderate‐certainty evidence), and digital registers (moderate‐certainty evidence) may have little or no effect on DTP3 uptake. Phone calls/SMS may have a very minimal effect on improving DTP3 uptake (low‐certainty evidence) and uptake of full vaccination (low‐certainty evidence).

Two studies targeted the providers of health care and involved training of health providers on supportive supervision. We are uncertain of the effects on OPV3 and HBV3 uptake (very low‐certainty evidence). Health system intervention studies included home visits, immunisation outreach alone, service‐level monetary support, pay for performance health system funding, and integration of immunisation with other services. We are uncertain of the effects of all these interventions on vaccination uptake (very low‐certainty evidence) except integration of immunisation services with other services. Integration with other services may improve vaccine uptake (low‐certainty evidence). Outreach alone or in combination with health education or non‐monetary incentives probably improves full vaccination among under fives (moderate‐certainty evidence).

Involving community leaders, in combination with training of health workers, probably improves the uptake of DTP3 and measles vaccine (moderate‐certainty evidence).

There was a dearth of data on outcomes like the occurrence of vaccine‐preventable diseases, the attitude of caregivers and clients towards immunisation, and adverse events.

Overall completeness and applicability of evidence

Immunisation coverage remains uneven between and within the world's regions and countries; in 2020, hepatitis B coverage was as high as 84% in the WHO Western Pacific Region and only 6% in the WHO African region (WHO 2021). A recent WHO report indicates a decline in global vaccination from 86% in 2019 to 83% in 2020 (WHO 2021). To address the stagnation in vaccine coverage, the Global Routine Immunisation Strategies and Practices (GRISP), a consortium of the World Health Organization and global immunisation partners, has developed a comprehensive framework to boost routine vaccinations. This framework aims to maximise the reach, managing vaccination programmes, mobilising people, and monitoring progress (WHO 2016). Interventions to improve coverage should focus on identified barriers within settings and be formulated within the framework. Studies that met the inclusion criteria in our systematic review were few and addressed limited aspects of the proposed GRISP framework. Of the six GRISP strategies to maximise reach, only integration of immunisation with other health services and capacity building of health workers were studied. GRISP identified nine activities to address the capacity building of health workers, among which only health worker training and supervision were among the interventions included in the review. There was a dearth of interventions on GRISP strategies for managing vaccination programmes (political commitment, planning and budgeting and mobilising resources for results and sustainability, national leadership and management, setting policy and guidance). This review included studies on mobilisation of the community and community participation in the delivery of vaccination services. Most included studies were on communicating vaccination messages. This spanned health education at health facility and community levels to the use of mobile health interventions. Mobile health (M‐health) was also used in monitoring the progress of vaccination through digital registers. Other aspects of mobilisation like interventions to address vaccine hesitancy and wrong perceptions about vaccines, and the consequences of adverse events, were not studied.

The use of M‐health interventions to boost uptake and improve coverage of immunisation services has gained increased recognition in the last decade (Dugas 2020; Grekin 2019). This highlights the role of technological advancement in supporting health care delivery. Inclusion of M‐health interventions is one of the new additions in this second update of this review. Thirteen of the 41 included studies implemented various M‐health interventions, including SMS and voice messages, tracking of children via a smartphone app, and a digital pendant. However, M‐health interventions are subject to access to or ownership of mobile phones, use of the same phone number throughout the study duration, and exposure to some level of education to understand written or voice messages, whether in local languages or English language. These socio‐economic factors remain key challenges in LMICs. A key consideration in implementing this intervention is the language characteristic of the intervention areas. In a mixed population where more than one local language is used, and a low literacy rate prevails, deploying SMS and voice messaging may become more demanding and challenging. Messages will have to be translated to these various languages, as opposed to sending out one message in a unified language to all study participants. This has implications for the cost and scalability of the intervention. In addition, M‐health interventions may be difficult to implement in settings where caregivers or households do not own a mobile phone; shared household phones provide no guarantee of the message being received by the targeted recipient. These challenges notwithstanding, most of the studies reported high rates of acceptability of the intervention by recipients with some willing to pay to get the SMS (Domek 2016). Some M‐health studies reported the inability of their systems to track if the caregivers received or read or listened to the messages (Dissieka 2019; Domek 2016; Domek 2019; Ekhaguere 2019). Therefore, bi‐directional messaging to allow confirmation of receipt of the messages by caregivers, especially in households with shared phones, may be more effective than one‐way communication interventions (Hall 2015; Wald 2015).

The interventions in the included studies varied enormously in content and in the intensity of delivery, raising questions about the likely impact of interventions in different settings and regarding how best to implement the interventions. For instance, how effective will a three‐minute health education intervention (Usman 2009; Usman 2011; low‐certainty evidence) be in a typical clinical setting in improving completion of the immunisation schedule? Will the same effect be obtained for more than one vaccine? How feasible is evidence‐based discussion (Andersson 2009) in a community with low literacy? How feasible is a monetary incentive intervention (Morris 2004) in a resource‐poor setting without donor support? Does the level of education of lay health workers proposed in two systematic reviews (Glenton 2011; Lewin 2010) affect outcomes? The limited number of studies makes it difficult to explore these issues and restricts the wider applicability of the evidence.

None of the included studies reported long‐term follow‐up data; this has implications for the sustainability of the interventions. Their long‐term effects could not also be ascertained. Studies that aimed at building the capacity of the providers (Amare 2021; Djibuti 2009; Morris 2004), and upgrading the physical structure (Morris 2004), could be said to be sustainable if other supporting resources are available. Experts have observed that a sustainability framework for projects aimed at strengthening immunisation systems in LMICs should include maintenance or continuance of health benefits from projects, institutionalisation of projects within the system, and capacity development (Gruen 2008; Shediac‐Rizkallah 1998). Early and active planning is also required (Shediac‐Rizkallah 1998). Sustainability of quality improvement interventions has been particularly challenging in LMICs, especially when a programme is supported by external funds (Gruen 2008). Withdrawal of external funds may not only impact negatively on the gains of the programme but may jeopardise support for future programmes (Gruen 2008). This is particularly so when the intervention is cost‐intensive. Studies exploring innovative funding mechanisms for vaccination are, therefore, required in LMICs.

Information on the resource implications of interventions may be helpful in determining their long‐term sustainability and cost‐effectiveness. Few included studies provided limited data on the cost of implementing the intervention (Andersson 2009; Banerjee 2010; Bangure 2015; Ekhaguere 2019; Powell‐Jackson 2018). Similarly, Corluka 2009 observed that studies included in the systematic reviews on lay health workers focussed more on health outcomes and did not adequately address affordability and sustainability; they were highly heterogeneous in terms of settings and outcomes, limiting their comparability. This observation underlies the findings of this review. Shea 2009 gives the cost of full vaccination of a child as varying between USD 1 and USD 40 in LMICs. This will much depend on the type of intervention and the context of the setting. Also, considering that the interventions assessed in this review were set up as parallel programmes, it is unclear how effective they will be if integrated with other services within the system, with the typical levels of human and other resources available. This calls for cost‐effectiveness evaluations of these interventions, particularly as integrated rather than stand‐alone programmes (Dicko 2011; Okwo‐Bele 2012). Such evaluations also have limitations as it can be difficult to translate these findings from one setting to another. Therefore, there is a need for study authors to provide the details of the required resources to implement the intervention.

Many immunisation programmes in LMICs are delivered as mass immunisation on set 'immunisation days', following mass immunisation campaigns (Balraj 1986; Bandyopadhyay 1996; Berry 1991; Cutts 1990; Gomber 1996; Kumar 1990; Lin 1971; Linkins 1995; Shaikh 2003). None of the reports of this commonly used strategy met the criteria for inclusion in our review or for the Saeterdal 2014 Cochrane Review on interventions aimed at communities to inform and/or educate on early childhood vaccination. Shea 2009 has noted that it may be difficult to randomise mass media interventions. However, interrupted time series designs (Nglazi 2014) and self‐controlled case series (SCCS) methods (Jean 2021) could be used to assess the effects of these mass immunisation campaigns on immunisation coverage.

Quality of the evidence

We used the GRADE approach to assess the certainty of evidence. The certainty of evidence was moderate for wearable reminders, immunisation outreach in combination with either community health education or non‐monetary incentives, and community leaders plus health provider intervention. It was low to moderate for health education, use of digital registers, and regular immunisation outreach alone; low for phone calls/SMS, integration of immunisation to other health services, supportive supervision; and very low for monetary incentives, home visits, and pay‐for‐performance funding. Overall, the certainty of the evidence for most interventions was low. The findings were commonly downgraded due to methodological limitations, heterogeneity, and having only one study. The main study limitations were non‐concealment of allocation, detection bias, lack of protection against contamination, and extraneous sources of bias. See Table 1; Table 2; Table 3; Table 4; Table 5; Table 6; Table 7; Table 8; Table 9; Table 10; Table 11 for the GRADE assessments. The low and very low certainty of evidence implies that the likelihood is high that the true effect of the interventions will be substantially different or very likely to be substantially different for the majority of the effects reported in this review.

We found limited information on the assessment of intervention costs, which limited our ability to summarise the impact of costs on immunisation coverage. None of the included studies reported adverse events.

Potential biases in the review process

We did not perform intention‐to‐treat analysis for missing individuals' data. However, we minimised bias in the process of conducting and reporting this review by adhering to standard Cochrane guidelines for conducting systematic reviews of interventions (Higgins 2023) and leads from the EPOC group. We conducted eligibility screening, data extraction, and risk of bias assessment in duplicate. A comprehensive database search was conducted by the Information Specialist of the EPOC group without any restrictions on the language or date of publication. However, access to studies was limited to those studies published in indexed journals. We did not perform handsearching; neither were non‐indexed local journals and grey literature searched. In addition, as noted by Machingaidze and colleagues, due to the broad nature of childhood immunisation (encompassing many different components), identifying a search strategy that includes all aspects of childhood immunisations is challenging (Machingaidze 2014). However, in one Cochrane Review on community‐aimed interventions to inform and educate about childhood vaccination, published in 2014, the authors did not identify additional studies to those included in this review (Saeterdal 2014).

Five of the authors of this review also authored one of the included studies (Oyo‐Ita 2021). The rest of the authors completed its data extraction, risk of bias, and GRADE assessment.

Agreements and disagreements with other studies or reviews

Several previous systematic reviews have assessed the effectiveness of interventions for improving childhood immunisation coverage (Batt 2004; Bordley 2000; Giles 2014; Glenton 2011; Jacobson Vann 2018; Johri 2015b; Kaufman 2013; Kendrick 2000; Palmer 2020, Pegurri 2005; Ryman 2008), although very few of them included studies from LMICs (Batt 2004; Glenton 2011; Pegurri 2005; Ryman 2008), and many were already out‐of‐date as the dates of the most recent searches for the reviews were pre‐2005 (Batt 2004; Bordley 2000; Kendrick 2000; Pegurri 2005), except Jacobson Vann 2018 and Palmer 2020.

The measures of effect for participant reminders agreed to some extent with the findings of Jacobson Vann 2018. Telephone calls, sending of letters and postcards, and speaking to clients in person improved the coverage of childhood vaccines in the participant reminder review (Jacobson Vann 2018). Similarly, Palmer 2020 reports that targeted client communication via a mobile device may increase child immunisation visits. In our review, the effect varied based on the type of reminder: while home‐based records (child vaccination card) alone or with health education, and phone/SMS, may improve vaccine uptake, wearable reminders and digital registers, on the other hand, did not.

We found very low‐certainty evidence that monetary incentives (in the form of vouchers, and conditional and unconditional cash transfers) have little or no effect on the uptake of vaccines. A systematic review on the effect of conditional cash transfers on health outcomes and the use of health services reported mixed results for the uptake of vaccination, but an improvement in the use of health services (Lagarde 2009). Two older (and now out‐of‐date) reviews reported that monetary incentives improved patient's compliance (Giuffrida 1997; Kane 2004), and that the effects varied with the goal of the incentive (Kane 2004). Another systematic review supported this view; monetary incentives increased attendance for vaccination and screening (Giles 2014). The differences between our review findings and those of this review may reflect differences across settings (high‐income compared to low‐ and middle‐income countries) or limitations of the studies included in our review.

In a related systematic review, Glenton and colleagues assessed the effects of lay or community health worker interventions on childhood immunisation coverage (Glenton 2011). Most of the included studies in the review showed that the use of lay or community health workers to promote immunisation uptake probably increased the number of children who were fully immunised. Our findings on the effect of community‐based health education and home visits were consistent with these findings.

In a review tagged 'strategies to increase the demand for childhood vaccination in low‐ and middle‐income countries: a systematic review and meta‐analysis', the authors concluded that, "demand‐side interventions are effective in improving the uptake of childhood vaccines delivered through routine immunization services in low‐ and middle‐income countries" (Johri 2015b). In this review we found engagement of traditional and religious leaders, an intervention intended for the leaders to drive increasing demand for vaccination, to have little or no effect.

Finally, our review is related to two other Cochrane Reviews (Kaufman 2013; Saeterdal 2014) conducted under the auspices of the 'Communicate to Vaccinate' project (Lewin 2011). Kaufman 2013 assessed the effects of face‐to‐face interventions for informing or educating parents about early childhood vaccination on immunisation uptake and parental knowledge, and Saeterdal 2014 reviewed interventions aimed at communities to inform or educate (or both) about early childhood vaccination. The two reviews included studies from any setting, while this review focused on studies from LMICs. We included three of the studies (Bolam 1998; Usman 2009; Usman 2011) included in the Kaufman 2013 review in our review and two studies (Andersson 2009; Pandey 2007) from our review were included in the Saeterdal 2014 review. While the findings of this review were similar to the findings of the Saeterdal 2014 review (i.e. that these interventions probably increase immunisation coverage), they differed from the findings of Kaufman 2013 that reported little or no improvement in immunisation coverage. This may be because Kaufman included studies from high‐, middle‐, and low‐income countries.

Authors' conclusions

Implications for practice.

Health education showed varying effects on the outcomes studied in this review, and the levels of certainty in the evidence differed. Facility‐based health education may be more effective in combination with the use of home‐based records, although the certainty of the evidence is low. Community‐based health education has a good prospect of addressing vaccine hesitancy and misconceptions about adverse events following vaccination. However, it has been observed that interventions such as community meetings may be cost‐intensive and so should be adopted with caution (Saeterdal 2014).

Based on the findings of this review, and supported by the findings of Jacobson Vann 2018 and Palmer 2020, the use of patient reminders (such as home‐based cards, phone calls/SMS) to boost childhood vaccination may improve uptake. Apart from the use of phones, other mobile health interventions have still been sparsely studied; most of the mobile health interventions were assessed in small, single studies. The evidence available on the use of mobile health interventions in low‐ and middle‐income countries is insufficient to inform practice.

Given the paucity and uncertainty of the evidence for health system interventions such as home visits and regular immunisation outreach sessions, more robust evaluation of their effectiveness is needed to inform practice.

The affordability and sustainability of monetary incentives is uncertain in low‐ and middle‐income countries, particularly when supported by external funds. Another review reported mixed effects of conditional cash transfer for immunisation uptake. It also suggested that conditional cash transfer may fail to improve coverage when other barriers to immunisation exist, noting that the impact is greater initially in low coverage areas (Lagarde 2009). Implementation in this setting may, therefore, need to be accompanied by rigorous evaluation.

The magnitude of the effects of the interventions was small and sustainability over long periods is uncertain; the certainty of the evidence also varied. The interventions assessed in this review should therefore be adopted with caution.

Implications for research.

The certainty of the evidence provided by the included studies ranged from very low to moderate. For this reason, our conclusions on the effectiveness of the interventions in this review are equivocal. The certainty of the evidence was downgraded for many interventions due to single studies contributing to the evidence; the number of participants was also often small. More studies and participants are required in the different subgroups. Rigorous studies providing high‐certainty evidence are required to inform vaccination practice in low‐ and middle‐income countries.

The magnitude of impact was small for most of the interventions. The impact of an intervention could be influenced by the baseline level of vaccine coverage; however, most studies did not provide this information. Settings with high levels of baseline vaccination coverage are not likely to see a significant impact, particularly when the duration of the intervention is short, as was the case with most of the included studies. Interventions with a long duration are needed to allow time for the impact of the intervention to take effect if vaccination coverage is already high. This would also facilitate the assessment of long‐term effects, as the short duration of interventions may obscure the assessment of an intervention's sustainability. Adopting an interrupted time series design for future studies may facilitate this.

Variability in the content and intensity of interventions affects the magnitude of their impact; standardisation of interventions is needed.

The currently available studies were often devoid of cost implications. The cost‐effectiveness of interventions should be incorporated into future studies to provide information on the financial resources required to deliver them, as their intensity and content will also determine cost.

The Global Routine Immunisation Strategies and Practices (GRISP) framework suggests some strategies for improving vaccination coverage; these need to be studied to provide evidence for practice.

What's new

Date	Event	Description
6 December 2023	New search has been performed	An additional 27 studies are included in this second update. These include mobile health interventions (digital register, phone calls/SMS), interventions targeting health providers, and engagement of community leaders. Recipient reminder was limited to redesigned card in the previous version. In this version, it includes stickers and wearable reminders and phone calls/SMS. Most of the additional studies assessed new interventions, so there was no change in the evidence for the included interventions.
6 December 2023	New citation required but conclusions have not changed	Most of the additional studies assessed new interventions, so there was no change in the evidence for the included interventions.

History

Protocol first published: Issue 4, 2009
Review first published: Issue 7, 2011

Date	Event	Description
22 June 2016	New search has been performed	This is the first update of the Cochrane Review published in 2011. We conducted a new search and added eight new studies to this update, and the conclusions have changed. We updated other content. New authors were also added.

Appendices

Appendix 1. Search strategies

Cochrane Central Register of Controlled Trials (CENTRAL 2022, Issue 3), part of Cochrane Library, Wiley (www.cochranelibrary.com/) (searched 11 July 2022)

No.	Search terms	Results
#1	MeSH descriptor: [Immunization] this term only	691
#2	MeSH descriptor: [Immunization Schedule] this term only	1157
#3	MeSH descriptor: [Immunization, Secondary] this term only	941
#4	MeSH descriptor: [Immunotherapy, Active] this term only	101
#5	MeSH descriptor: [Mass Vaccination] this term only	40
#6	MeSH descriptor: [Immunization Programs] this term only	202
#7	MeSH descriptor: [Vaccination] this term only	2811
#8	MeSH descriptor: [Vaccination Coverage] this term only	31
#9	#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8	4965
#10	MeSH descriptor: [Child] explode all trees	61542
#11	MeSH descriptor: [Infant] explode all trees	34960
#12	MeSH descriptor: [Mothers] this term only	2193
#13	MeSH descriptor: [Women] this term only	248
#14	MeSH descriptor: [Pregnant Women] this term only	480
#15	#10 or #11 or #12 or #13 or #14	82076
#16	#9 and #15	2480
#17	(immunization or immunisation or vaccination) next (program* or rate* or coverage or adher*):ti	315
#18	(vaccinat* or revaccinat* or immunization or immunisation) near/3 (child* or infant* or newborn* or neonat* or baby or babies or kid or kids or toddler* or woman or women or mother or mothers):ti,ab,kw	3469
#19	#16 or #17 or #18	5177
#20	(Africa or Asia or Caribbean or "West Indies" or "South America" or "Latin America" or "Central America"):ti,ab,kw	13832
#21	(Afghanistan or Albania or Algeria or Angola or Antigua or Barbuda or Argentina or Armenia or Armenian or Aruba or Azerbaijan or Bahrain or Bangladesh or Barbados or Benin or Byelarus or Byelorussian or Belarus or Belorussian or Belorussia or Belize or Bhutan or Bolivia or Bosnia or Herzegovina or Hercegovina or Botswana or Brazil or Brasil or Bulgaria or "Burkina Faso" or "Burkina Fasso" or "Upper Volta" or Burundi or Urundi or Cambodia or "Khmer Republic" or Kampuchea or Cameroon or Cameroons or Cameron or Camerons or "Cape Verde" or "Central African Republic" or Chad or Chile or China or Colombia or Comoros or "Comoro Islands" or Comores or Mayotte or Congo or Zaire or "Costa Rica" or "Cote d'Ivoire" or "Ivory Coast" or Croatia or Cuba or Cyprus or Czechoslovakia or "Czech Republic" or Slovakia or "Slovak Republic"):ti,ab,kw	32468
#22	(Djibouti or "French Somaliland" or Dominica or "Dominican Republic" or "East Timor" or "East Timur" or "Timor Leste" or Ecuador or Egypt or "United Arab Republic" or "El Salvador" or Eritrea or Estonia or Ethiopia or Fiji or Gabon or "Gabonese Republic" or Gambia or Gaza or Georgia or Georgian or Ghana or "Gold Coast" or Greece or Grenada or Guatemala or Guinea or Guam or Guiana or Guyana or Haiti or Honduras or Hungary or India or Maldives or Indonesia or Iran or Iraq or "Isle of Man" or Jamaica or Jordan or Kazakhstan or Kazakh or Kenya or Kiribati or Korea or Kosovo or Kyrgyzstan or Kirghizia or "Kyrgyz Republic" or Kirghiz or Kirgizstan or "Lao PDR" or Laos or Latvia or Lebanon or Lesotho or Basutoland or Liberia or Libya or Lithuania):ti,ab,kw	41449
#23	(Macedonia or Madagascar or "Malagasy Republic" or Malaysia or Malaya or Malay or Sabah or Sarawak or Malawi or Nyasaland or Mali or Malta or "Marshall Islands" or Mauritania or Mauritius or "Agalega Islands" or Mexico or Micronesia or "Middle East" or Moldova or Moldovia or Moldovian or Mongolia or Montenegro or Morocco or Ifni or Mozambique or Myanmar or Myanma or Burma or Namibia or Nepal or "Netherlands Antilles" or "New Caledonia" or Nicaragua or Niger or Nigeria or "Northern Mariana Islands" or Oman or Muscat or Pakistan or Palau or Palestine or Panama or Paraguay or Peru or Philippines or Philipines or Phillipines or Phillippines or Poland or Portugal or "Puerto Rico"):ti,ab,kw	17150
#24	(Romania or Rumania or Roumania or Russia or Russian or Rwanda or Ruanda or "Saint Kitts" or "St Kitts" or Nevis or "Saint Lucia" or "St Lucia" or "Saint Vincent" or "St Vincent" or Grenadines or Samoa or "Samoan Islands" or "Navigator Island" or "Navigator Islands" or "Sao Tome" or "Saudi Arabia" or Senegal or Serbia or Montenegro or Seychelles or "Sierra Leone" or Slovenia or "Sri Lanka" or Ceylon or "Solomon Islands" or Somalia or Sudan or Suriname or Surinam or Swaziland or Syria or Tajikistan or Tadzhikistan or Tadjikistan or Tadzhik or Tanzania or Thailand or Togo or "Togolese Republic" or Tonga or Trinidad or Tobago or Tunisia or Turkey or Turkmenistan or Turkmen or Uganda or Ukraine or Uruguay or USSR or "Soviet Union" or "Union of Soviet Socialist Republics" or Uzbekistan or Uzbek or Vanuatu or "New Hebrides" or Venezuela or Vietnam or "Viet Nam" or "West Bank" or Yemen or Yugoslavia or Zambia or Zimbabwe or Rhodesia):ti,ab,kw	18701
#25	(developing or less* next developed or "under developed" or underdeveloped or "middle income" or low* next income or underserved or "under served" or deprived or poor*) next (countr* or nation* or population* or world):ti,ab,kw	8181
#26	(developing or less* next developed or "under developed" or underdeveloped or "middle income" or low* next income) next (economy or economies):ti,ab,kw	22
#27	low* next (gdp or gnp or "gross domestic" or "gross national"):ti,ab,kw	48
#28	(low near/3 middle near/3 countr*):ti,ab,kw	1939
#29	(lmic or lmics or "third world" or "lami country" or "lami countries"):ti,ab,kw	643
#30	("transitional country" or "transitional countries"):ti,ab,kw	5
#31	(#20 or #21 or #22 or #23 or #24 or #25 or #26 or #27 or #28 or #29 or #30)	113064
#32	#19 and #31 in Trials	1826

Ovid MEDLINE(R) ALL <1946 to July 08, 2022> (searched 11 July 2022)

No.	Search terms	Results
1	Immunization/	52999
2	Immunization Schedule/	11378
3	Immunization, Secondary/	8879
4	Immunotherapy, Active/	2493
5	Mass Immunization/	3486
6	Immunization Programs/	12465
7	Vaccination/	97213
8	Vaccination Coverage/	2148
9	or/1‐8	168947
10	exp Child/	2086962
11	exp Infant/	1223438
12	Mothers/	52175
13	Women/	15147
14	Pregnant Women/	12489
15	or/10‐14	2735264
16	9 and 15	41580
17	((vaccinat* or revaccinat* or immunization or immunisation) adj3 (child* or infant? or newborn? or neonat* or baby or babies or kid? or toddler? or woman or women or mother?)).ti,ab,kf.	24505
18	((immunization or immunisation or vaccination) adj (program* or rate* or coverage or adher*)).ti.	6184
19	16 or 17 or 18	56959
20	Developing Countries.sh,kf.	91410
21	(Africa or Asia or Caribbean or West Indies or South America or Latin America or Central America).hw,kf,ti,ab,cp.	322694
22	(Afghanistan or Albania or Algeria or Angola or Antigua or Barbuda or Argentina or Armenia or Armenian or Aruba or Azerbaijan or Bahrain or Bangladesh or Barbados or Benin or Byelarus or Byelorussian or Belarus or Belorussian or Belorussia or Belize or Bhutan or Bolivia or Bosnia or Herzegovina or Hercegovina or Botswana or Brazil or Brasil or Bulgaria or Burkina Faso or Burkina Fasso or Upper Volta or Burundi or Urundi or Cambodia or Khmer Republic or Kampuchea or Cameroon or Cameroons or Cameron or Camerons or Cape Verde or Central African Republic or Chad or Chile or China or Colombia or Comoros or Comoro Islands or Comores or Mayotte or Congo or Zaire or Costa Rica or Cote d'Ivoire or Ivory Coast or Croatia or Cuba or Cyprus or Czechoslovakia or Czech Republic or Slovakia or Slovak Republic or Djibouti or French Somaliland or Dominica or Dominican Republic or East Timor or East Timur or Timor Leste or Ecuador or Egypt or United Arab Republic or El Salvador or Eritrea or Estonia or Ethiopia or Fiji or Gabon or Gabonese Republic or Gambia or Gaza or Georgia Republic or Georgian Republic or Ghana or Gold Coast or Greece or Grenada or Guatemala or Guinea or Guam or Guiana or Guyana or Haiti or Honduras or Hungary or India or Maldives or Indonesia or Iran or Iraq or Isle of Man or Jamaica or Jordan or Kazakhstan or Kazakh or Kenya or Kiribati or Korea or Kosovo or Kyrgyzstan or Kirghizia or Kyrgyz Republic or Kirghiz or Kirgizstan or Lao PDR or Laos or Latvia or Lebanon or Lesotho or Basutoland or Liberia or Libya or Lithuania or Macedonia or Madagascar or Malagasy Republic or Malaysia or Malaya or Malay or Sabah or Sarawak or Malawi or Nyasaland or Mali or Malta or Marshall Islands or Mauritania or Mauritius or Agalega Islands or Mexico or Micronesia or Middle East or Moldova or Moldovia or Moldovian or Mongolia or Montenegro or Morocco or Ifni or Mozambique or Myanmar or Myanma or Burma or Namibia or Nepal or Netherlands Antilles or New Caledonia or Nicaragua or Niger or Nigeria or Northern Mariana Islands or Oman or Muscat or Pakistan or Palau or Palestine or Panama or Paraguay or Peru or Philippines or Philipines or Phillipines or Phillippines or Poland or Portugal or Puerto Rico or Romania or Rumania or Roumania or Russia or Russian or Rwanda or Ruanda or Saint Kitts or St Kitts or Nevis or Saint Lucia or St Lucia or Saint Vincent or St Vincent or Grenadines or Samoa or Samoan Islands or Navigator Island or Navigator Islands or Sao Tome or Saudi Arabia or Senegal or Serbia or Montenegro or Seychelles or Sierra Leone or Slovenia or Sri Lanka or Ceylon or Solomon Islands or Somalia or Sudan or Suriname or Surinam or Swaziland or Syria or Tajikistan or Tadzhikistan or Tadjikistan or Tadzhik or Tanzania or Thailand or Togo or Togolese Republic or Tonga or Trinidad or Tobago or Tunisia or Turkey or Turkmenistan or Turkmen or Uganda or Ukraine or Uruguay or USSR or Soviet Union or Union of Soviet Socialist Republics or Uzbekistan or Uzbek or Vanuatu or New Hebrides or Venezuela or Vietnam or Viet Nam or West Bank or Yemen or Yugoslavia or Zambia or Zimbabwe or Rhodesia).hw,kf,ti,ab,cp.	4076834
23	((developing or less* developed or under developed or underdeveloped or middle income or low* income or underserved or under served or deprived or poor*) adj (countr* or nation? or population? or world)).ti,ab.	122720
24	((developing or less* developed or under developed or underdeveloped or middle income or low* income) adj (economy or economies)).ti,ab.	824
25	(low* adj (gdp or gnp or gross domestic or gross national)).ti,ab.	314
26	(low adj3 middle adj3 countr*).ti,ab.	25440
27	(lmic or lmics or third world or lami countr*).ti,ab.	11008
28	transitional countr*.ti,ab.	175
29	or/20‐28	4312143
30	19 and 29	19334
31	randomized controlled trial.pt.	572472
32	controlled clinical trial.pt.	94938
33	pragmatic clinical trial.pt.	2119
34	multicenter study.pt.	323336
35	non‐randomized controlled trials as topic/	1047
36	interrupted time series analysis/	1659
37	controlled before‐after studies/	699
38	(randomis* or randomiz* or randomly allocat* or random allocat*).ti,ab.	769053
39	groups.ab.	2376408
40	(trial or impact or effect or multicenter or multi center or multicentre or multi centre).ti.	1557028
41	(intervention* or controlled or control group? or (before adj5 after) or (pre adj5 post) or pretest or pre test or posttest or post test or quasiexperiment* or quasi experiment* or evaluat* or time series or time point? or repeated measur*).ti,ab.	6256139
42	or/31‐41	8751629
43	exp Animals/	25629738
44	Humans/	20604224
45	43 not (43 and 44)	5025514
46	review.pt.	3011335
47	meta analysis.pt.	163588
48	news.pt.	213393
49	comment.pt.	970355
50	editorial.pt.	610622
51	cochrane database of systematic reviews.jn.	15911
52	comment on.cm.	970302
53	(systematic review or literature review).ti.	234449
54	or/45‐53	9539804
55	42 not 54	6604356
56	30 and 55	7661

CINAHL 1981‐present, EbscoHost (searched 11 July 2022)

No.	Search terms	Results
S54	S16 AND S34 AND S52 [Limiters ‐ Exclude MEDLINE records]	923
S53	S16 AND S34 AND S52	3.041
S52	S35 OR S36 OR S37 OR S38 OR S39 OR S40 OR S41 OR S42 OR S43 OR S44 OR S45 OR S46 OR S47 OR S48 OR S49 OR S50 OR S51	3.012.637
S51	TI (randomis* or randomiz* or randomly or trial or effect* or impact* or intervention* or multicenter or "multi center" or multicentre or "multi centre" or controlled or groups or before N5 after or pre N5 post or ((pretest or "pre test") and (posttest or "post test")) or quasiexperiment* or quasi W0 experiment* or pseudo experiment* or pseudoexperiment* or evaluat* or "time series" or time W0 point* or repeated W0 measur*) OR AB (randomis* or randomiz* or randomly or trial or effect* or impact* or intervention* or multicenter or "multi center" or multicentre or "multi centre" or controlled or groups or before N5 after or pre N5 post or ((pretest or "pre test") and (posttest or "post test")) or quasiexperiment* or quasi W0 experiment* or evaluat* or "time series" or time W0 point* or repeated W0 measur*)	2.839.333
S50	(MH "Health Services Research")	16.391
S49	(MH "Experimental Studies+")	400.556
S48	(MH "Time Series")	3.052
S47	(MH "Multiple Time Series")	17
S46	(MH "Interrupted Time Series Analysis")	777
S45	(MH "Repeated Measures")	54.988
S44	(MH "Multicenter Studies")	343.672
S43	(MH "Quasi‐Experimental Studies")	15.043
S42	(MH "Pretest‐Posttest Design")	49.689
S41	(MH "Pretest‐Posttest Control Group Design")	1.186
S40	(MH "Nonrandomized Trials")	768
S39	(MH "Intervention Trials")	7.745
S38	(MH "Clinical Trials")	183.365
S37	(MH "Randomized Controlled Trials")	129.893
S36	PT clinical trial	111.274
S35	PT randomized controlled trial	143.187
S34	S17 OR S18 OR S19 OR S20 OR S21 OR S22 OR S23 OR S24 OR S25 OR S26 OR S27 OR S28 OR S29 OR S30 OR S31 OR S32 OR S33	677.033
S33	TI transitional W0 countr* OR AB transitional W0 countr*	85
S32	TI ( lmic or lmics or third W0 world or lami W0 countr* ) OR AB ( lmic or lmics or third W0 world or lami W0 countr* )	3.743
S31	TI low N3 middle N3 countr* OR AB low N3 middle N3 countr*	11.241
S30	TI ( low* W0 (gdp or gnp or gross W0 domestic or gross W0 national) ) OR AB ( low* W0 (gdp or gnp or gross W0 domestic or gross W0 national) )	78
S29	TI ( (developing or less* W0 developed or under W0 developed or underdeveloped or middle W0 income or low* W0 income) W0 (economy or economies) ) OR AB ( (developing or less* W0 developed or under W0 developed or underdeveloped or middle W0 income or low* W0 income) W0 (economy or economies) )	169
S28	TI ( (developing or less* W0 developed or under W0 developed or underdeveloped or middle W0 income or low* W0 income or underserved or under W0 served or deprived or poor*) W0 (countr* or nation or nations or population* or world or area or areas) ) OR AB ( (developing or less* W0 developed or under W0 developed or underdeveloped or middle W0 income or low* W0 income or underserved or under W0 served or deprived or poor*) W0 (countr* or nation or nations or population* or world or area or areas) )	42.309
S27	MW ( Afghanistan or Bangladesh or Benin or "Burkina Faso" or Burundi or Cambodia or "Central African Republic" or Chad or Comoros or Congo or "Cote d'Ivoire" or Eritrea or Ethiopia or Gambia or Ghana or Guinea or Haiti or India or Kenya or Korea or Kyrgyz or Kyrgyzstan or Lao or Laos or Liberia or Madagascar or Malawi or Mali or Mauritania or Melanesia or Mongolia or Mozambique or Burma or Myanmar or Nepal or Niger or Nigeria or Pakistan or Rwanda or "Salomon Islands" or "Sao Tome" or Senegal or "Sierra Leone" or Somalia or Sudan or Tajikistan or Tanzania or Timor or Togo or Uganda or Uzbekistan or Vietnam or "Viet Nam" or Yemen or Zambia or Zimbabwe ) or TI ( Afghanistan or Bangladesh or Benin or "Burkina Faso" or Burundi or Cambodia or "Central African Republic" or Chad or Comoros or Congo or "Cote d'Ivoire" or Eritrea or Ethiopia or Gambia or Ghana or Guinea or Haiti or India or Kenya or Korea or Kyrgyz or Kyrgyzstan or Lao or Laos or Liberia or Madagascar or Malawi or Mali or Mauritania or Melanesia or Mongolia or Mozambique or Burma or Myanmar or Nepal or Niger or Nigeria or Pakistan or Rwanda or "Salomon Islands" or "Sao Tome" or Senegal or "Sierra Leone" or Somalia or Sudan or Tajikistan or Tanzania or Timor or Togo or Uganda or Uzbekistan or Vietnam or "Viet Nam" or Yemen or Zambia or Zimbabwe ) or AB ( Afghanistan or Bangladesh or Benin or "Burkina Faso" or Burundi or Cambodia or "Central African Republic" or Chad or Comoros or Congo or "Cote d'Ivoire" or Eritrea or Ethiopia or Gambia or Ghana or Guinea or Haiti or India or Kenya or Korea or Kyrgyz or Kyrgyzstan or Lao or Laos or Liberia or Madagascar or Malawi or Mali or Mauritania or Melanesia or Mongolia or Mozambique or Burma or Myanmar or Nepal or Niger or Nigeria or Pakistan or Rwanda or "Salomon Islands" or "Sao Tome" or Senegal or "Sierra Leone" or Somalia or Sudan or Tajikistan or Tanzania or Timor or Togo or Uganda or Uzbekistan or Vietnam or "Viet Nam" or Yemen or Zambia or Zimbabwe )	178.821
S26	MW ( Albania or Algeria or Angola or Armenia or Azerbaijan or Belarus or Bhutan or Bolivia or Bosnia or Herzegovina or "Cape Verde" or Cameroon or China or Colombia or Congo or Cuba or Djibouti or "Dominican Republic" or Ecuador or Egypt or "El Salvador" or Fiji or Gaza or Georgia or Guam or Guatemala or Guyana or Honduras or "Indian Ocean Islands" or Indonesia or Iran or Iraq or Jamaica or Jordan or Kiribati or Lesotho or Macedonia or Maldives or "Marshall Islands" or Micronesia or "Middle East" or Moldova or Morocco or Namibia or Nicaragua or Palestin* or Paraguay or Peru or Philippines or Samoa or "Sri Lanka" or Suriname or Swaziland or Syria or "Syrian Arab Republic" or Thailand or Tonga or Tunisia or Turkmenistan or Ukraine or Vanuatu or "West Bank" ) or TI ( Albania or Algeria or Angola or Armenia or Azerbaijan or Belarus or Bhutan or Bolivia or Bosnia or Herzegovina or "Cape Verde" or Cameroon or China or Colombia or Congo or Cuba or Djibouti or "Dominican Republic" or Ecuador or Egypt or "El Salvador" or Fiji or Gaza or Georgia or Guam or Guatemala or Guyana or Honduras or "Indian Ocean Islands" or Indonesia or Iran or Iraq or Jamaica or Jordan or Kiribati or Lesotho or Macedonia or Maldives or "Marshall Islands" or Micronesia or "Middle East" or Moldova or Morocco or Namibia or Nicaragua or Palestin* or Paraguay or Peru or Philippines or Samoa or "Sri Lanka" or Suriname or Swaziland or Syria or "Syrian Arab Republic" or Thailand or Tonga or Tunisia or Turkmenistan or Ukraine or Vanuatu or "West Bank" ) or AB ( Albania or Algeria or Angola or Armenia or Azerbaijan or Belarus or Bhutan or Bolivia or Bosnia or Herzegovina or "Cape Verde" or Cameroon or China or Colombia or Congo or Cuba or Djibouti or "Dominican Republic" or Ecuador or Egypt or "El Salvador" or Fiji or Gaza or Georgia or Guam or Guatemala or Guyana or Honduras or "Indian Ocean Islands" or Indonesia or Iran or Iraq or Jamaica or Jordan or Kiribati or Lesotho or Macedonia or Maldives or "Marshall Islands" or Micronesia or "Middle East" or Moldova or Morocco or Namibia or Nicaragua or Palestin* or Paraguay or Peru or Philippines or Samoa or "Sri Lanka" or Suriname or Swaziland or Syria or "Syrian Arab Republic" or Thailand or Tonga or Tunisia or Turkmenistan or Ukraine or Vanuatu or "West Bank" )	203.543
S25	MW ( "American Samoa" or Argentina or Belize or Botswana or Brazil or Brasil or Bulgaria or Chile or Comoros or "Costa Rica" or Croatia or Dominica or Guinea or Gabon or Grenada or Grenadines or Hungary or Kazakhstan or Latvia or Lebanon or Libia or libyan or Libya or Lithuania or Malaysia or Mauritius or Mayotte or Mexico or Micronesia or Montenegro or Nevis or "Northern Mariana Islands" or Oman or Palau or Panama or Poland or Romania or Russia or "Russian Federation" or Samoa or "Saint Lucia" or "St Lucia" or "Saint Kitts" or "St Kitts" or "Saint Vincent" or "St Vincent" or Serbia or Seychelles or Slovakia or "Slovak Republic" or "South Africa" or Turkey or Uruguay or Venezuela or Yugoslavia ) or TI ( "American Samoa" or Argentina or Belize or Botswana or Brazil or Bulgaria or Chile or Comoros or "Costa Rica" or Croatia or Dominica or Guinea or Gabon or Grenada or Grenadines or Hungary or Kazakhstan or Latvia or Lebanon or Libia or libyan or Libya or Lithuania or Malaysia or Mauritius or Mayotte or Mexico or Micronesia or Montenegro or Nevis or "Northern Mariana Islands" or Oman or Palau or Panama or Poland or Romania or Russia or "Russian Federation" or Samoa or "Saint Lucia" or "St Lucia" or "Saint Kitts" or "St Kitts" or "Saint Vincent" or "St Vincent" or Serbia or Seychelles or Slovakia or "Slovak Republic" or "South Africa" or Turkey or Uruguay or Venezuela or Yugoslavia ) or AB ( "American Samoa" or Argentina or Belize or Botswana or Brazil or Bulgaria or Chile or Comoros or "Costa Rica" or Croatia or Dominica or Guinea or Gabon or Grenada or Grenadines or Hungary or Kazakhstan or Latvia or Lebanon or Libia or libyan or Libya or Lithuania or Malaysia or Mauritius or Mayotte or Mexico or Micronesia or Montenegro or Nevis or "Northern Mariana Islands" or Oman or Palau or Panama or Poland or Romania or Russia or "Russian Federation" or Samoa or "Saint Lucia" or "St Lucia" or "Saint Kitts" or "St Kitts" or "Saint Vincent" or "St Vincent" or Serbia or Seychelles or Slovakia or "Slovak Republic" or "South Africa" or Turkey or Uruguay or Venezuela or Yugoslavia )	179.243
S24	TI ( Africa or Asia or "South America" or "Latin America" or "Central America" ) or AB ( Africa or Asia or "South America" or "Latin America" or "Central America" )	52.444
S23	(MH "Asia+")	328.566
S22	(MH "West Indies+")	11.084
S21	(MH "South America+")	67.917
S20	(MH "Latin America")	3.317
S19	(MH "Central America+")	4.521
S18	(MH "Africa+")	94.828
S17	(MH "Developing Countries")	19.862
S16	S13 OR S14 OR S15	19.013
S15	TI (immunization or immunisation or vaccination) W0 (program* or rate* or coverage or adher*)	2.729
S14	TI ( (vaccinat* or revaccinat* or immunization or immunisation) N3 (child* or infant or infants or newborn or neonat* or baby or babies or kid or kids or toddler* or woman or women or mother*) ) OR AB ( (vaccinat* or revaccinat* or immunization or immunisation) N3 (child* or infant or infants or newborn or neonat* or baby or babies or kid or kids or toddler* or woman or women or mother*) )	9.005
S13	S5 AND S12	12.716
S12	S6 OR S7 OR S8 OR S9 OR S10 OR S11	730.564
S11	(MH "Expectant Mothers")	11.469
S10	(MH "Women")	22.388
S9	(MH "Mothers")	35.111
S8	(MH "Infant, Newborn")	141.864
S7	(MH "Infant")	185.508
S6	(MH "Child")	509.979
S5	S1 or S2 or S3 or S4	47.549
S4	(MH "Immunization Programs")	6.448
S3	(MH "Immunotherapy")	12.674
S2	(MH "Immunization Schedule")	3.309
S1	(MH "Immunization") or (MH "Vaccination Coverage")	28.954

	Embase 1980 to 2014 Week 34, Ovid (searched 2 September 2014)
#	Searches	Results
1	Immunization/	75652
2	Active Immunization/	6595
3	Mass Immunization/	2421
4	Vaccination/	96045
5	Revaccination/	1059
6	(vaccinat$ or revaccinat$ or immunization or immunisation or immunotherapy).tw.	226888
7	or/1‐6	289620
8	Tetanus Prophylaxis/	1259
9	BCG Vaccination/	7072
10	Measles Vaccination/	2189
11	or/8‐10	10339
12	Tetanus Toxoid/	10548
13	Diphtheria Toxoid/	2535
14	Diphtheria Toxoid crm197/	216
15	Diphtheria Tetanus Toxoid/	427
16	BCG Vaccine/	27645
17	Diphtheria Pertussis Poliomyelitis Tetanus Haemophilus Influenzae Type B Hepatitis B Vaccine/	380
18	Diphtheria Pertussis Poliomyelitis Tetanus Vaccine/	393
19	Diphtheria Pertussis Tetanus Haemophilus Influenzae Type B Hepatitis B Vaccine/	158
20	Diphtheria Pertussis Tetanus Haemophilus Influenzae Type B Vaccine/	464
21	Diphtheria Pertussis Tetanus Vaccine/	6524
22	Diphtheria Poliomyelitis Tetanus Vaccine/	74
23	Diphtheria Tetanus Vaccine/	675
24	Diphtheria Vaccine/	1902
25	Haemophilus Influenzae Type B Hepatitis B Vaccine/	230
26	Haemophilus Influenzae Type B Vaccine/	4269
27	Haemophilus Influenzae Vaccine/	944
28	Haemophilus Vaccine/	764
29	Pertussis Vaccine/	6378
30	Triple Vaccine/	715
31	Hepatitis a Hepatitis B Vaccine/	502
32	Hepatitis B Vaccine/	15773
33	Hepatitis Vaccine/	2126
34	Recombinant Hepatitis B Vaccine/	1776
35	Measles Mumps Rubella Vaccine/	5594
36	Measles Mumps Vaccine/	102
37	Measles Rubella Vaccine/	100
38	Measles Vaccine/	7860
39	Mumps Vaccine/	2031
40	Rubella Vaccine/	3477
41	Chickenpox Measles Mumps Rubella Vaccine/	219
42	Poliomyelitis Vaccine/	7207
43	Oral Poliomyelitis Vaccine/	4250
44	((tetanus or diphtheria) adj toxoid).tw.	5484
45	((tetanus or diphtheria? or pertussis or whooping cough or measles or mumps or rubella? or rubeola or mmr or polio$ or tuberculosis or tuberculoses or bcg or calmette$ or hepatitis b or haemophilus or triple) adj vaccine?).tw.	17760
46	or/12‐45	86597
47	Tetanus/	12351
48	Diphtheria/	9102
49	Measles/	15582
50	Mumps/	5967
51	Rubella/	9019
52	Pertussis/	10521
53	Poliomyelitis/	18525
54	Tuberculosis/	89886
55	Lung Tuberculosis/	63542
56	Mycobacterium Tuberculosis/	48597
57	Hepatitis B/	69010
58	Chronic Hepatitis/	21541
59	Haemophilus Influenzae/	18964
60	Haemophilus Influenzae Type B/	3868
61	(tetanus or diphtheria? or measles or rubella? or rubeola or mumps or epidemic parotit$ or pertussis or whooping cough or polio$ or infantile paralysis or tuberculosis or tuberculoses or hepatitis b or haemophilus influenza?).tw.	333094
62	or/47‐61	440846
63	exp Child/	2005016
64	exp Newborn/	450384
65	Child Care/	30274
66	(child$ or infant? or newborn? or neonat$ or baby or babies or kid? or toddler?).tw.	1614491
67	or/63‐66	2499583
68	7 and (Tetanus/ or tetanus.tw.)	10450
69	Tetanus Toxoid/ or Tetanus Prophylaxis/ or (tetanus toxoid or tetanus vaccin$ or tetanus prophylaxis).tw.	13141
70	or/68‐69	18159
71	exp Mother/	86127
72	Female/	5983316
73	(woman or women or mother? or female?).tw.	1819414
74	or/71‐73	6295611
75	70 and 74	5326
76	Developing Country.sh.	75918
77	(Africa or Asia or Caribbean or West Indies or South America or Latin America or Central America).hw,ti,ab,cp.	227844
78	(Afghanistan or Albania or Algeria or Angola or Antigua or Barbuda or Argentina or Armenia or Armenian or Aruba or Azerbaijan or Bahrain or Bangladesh or Barbados or Benin or Byelarus or Byelorussian or Belarus or Belorussian or Belorussia or Belize or Bhutan or Bolivia or Bosnia or Herzegovina or Hercegovina or Botswana or Brazil or Brasil or Bulgaria or Burkina Faso or Burkina Fasso or Upper Volta or Burundi or Urundi or Cambodia or Khmer Republic or Kampuchea or Cameroon or Cameroons or Cameron or Camerons or Cape Verde or Central African Republic or Chad or Chile or China or Colombia or Comoros or Comoro Islands or Comores or Mayotte or Congo or Zaire or Costa Rica or Cote d'Ivoire or Ivory Coast or Croatia or Cuba or Cyprus or Czechoslovakia or Czech Republic or Slovakia or Slovak Republic or Djibouti or French Somaliland or Dominica or Dominican Republic or East Timor or East Timur or Timor Leste or Ecuador or Egypt or United Arab Republic or El Salvador or Eritrea or Estonia or Ethiopia or Fiji or Gabon or Gabonese Republic or Gambia or Gaza or Georgia Republic or Georgian Republic or Ghana or Gold Coast or Greece or Grenada or Guatemala or Guinea or Guam or Guiana or Guyana or Haiti or Honduras or Hungary or India or Maldives or Indonesia or Iran or Iraq or Isle of Man or Jamaica or Jordan or Kazakhstan or Kazakh or Kenya or Kiribati or Korea or Kosovo or Kyrgyzstan or Kirghizia or Kyrgyz Republic or Kirghiz or Kirgizstan or Lao PDR or Laos or Latvia or Lebanon or Lesotho or Basutoland or Liberia or Libya or Lithuania or Macedonia or Madagascar or Malagasy Republic or Malaysia or Malaya or Malay or Sabah or Sarawak or Malawi or Nyasaland or Mali or Malta or Marshall Islands or Mauritania or Mauritius or Agalega Islands or Mexico or Micronesia or Middle East or Moldova or Moldovia or Moldovian or Mongolia or Montenegro or Morocco or Ifni or Mozambique or Myanmar or Myanma or Burma or Namibia or Nepal or Netherlands Antilles or New Caledonia or Nicaragua or Niger or Nigeria or Northern Mariana Islands or Oman or Muscat or Pakistan or Palau or Palestine or Panama or Paraguay or Peru or Philippines or Philipines or Phillipines or Phillippines or Poland or Portugal or Puerto Rico or Romania or Rumania or Roumania or Russia or Russian or Rwanda or Ruanda or Saint Kitts or St Kitts or Nevis or Saint Lucia or St Lucia or Saint Vincent or St Vincent or Grenadines or Samoa or Samoan Islands or Navigator Island or Navigator Islands or Sao Tome or Saudi Arabia or Senegal or Serbia or Montenegro or Seychelles or Sierra Leone or Slovenia or Sri Lanka or Ceylon or Solomon Islands or Somalia or Sudan or Suriname or Surinam or Swaziland or Syria or Tajikistan or Tadzhikistan or Tadjikistan or Tadzhik or Tanzania or Thailand or Togo or Togolese Republic or Tonga or Trinidad or Tobago or Tunisia or Turkey or Turkmenistan or Turkmen or Uganda or Ukraine or Uruguay or USSR or Soviet Union or Union of Soviet Socialist Republics or Uzbekistan or Uzbek or Vanuatu or New Hebrides or Venezuela or Vietnam or Viet Nam or West Bank or Yemen or Yugoslavia or Zambia or Zimbabwe or Rhodesia).hw,ti,ab,cp.	2838905
79	((developing or less* developed or under developed or underdeveloped or middle income or low* income or underserved or under served or deprived or poor*) adj (countr* or nation? or population? or world)).ti,ab.	68123
80	((developing or less* developed or under developed or underdeveloped or middle income or low* income) adj (economy or economies)).ti,ab.	351
81	(low* adj (gdp or gnp or gross domestic or gross national)).ti,ab.	187
82	(low adj3 middle adj3 countr*).ti,ab.	4139
83	(lmic or lmics or third world or lami countr*).ti,ab.	3741
84	transitional countr*.ti,ab.	138
85	or/76‐84	3019888
86	Randomized Controlled Trial/	348266
87	Controlled Clinical Trial/	386406
88	Quasi Experimental Study/	2013
89	Pretest Posttest Control Group Design/	206
90	Time Series Analysis/	14239
91	Experimental Design/	10019
92	Multicenter Study/	109759
93	(randomis* or randomiz* or randomly or random allocat*).ti,ab.	727521
94	groups.ab.	1698086
95	(trial or multicentre or multicenter or multi centre or multi center).ti.	192503
96	(intervention* or controlled or control group or compare or compared or (before adj5 after) or (pre adj5 post) or pretest or pre test or posttest or post test or quasiexperiment* or quasi experiment* or evaluat* or effect or impact or time series or time point? or repeated measur*).ti,ab.	8028793
97	or/86‐96	8766538
98	(systematic review or literature review).ti.	62313
99	"cochrane database of systematic reviews".jn.	3777
100	Nonhuman/	4359920
101	or/98‐100	4424301
102	97 not 101	6927465
103	7 and 62 and 67 and 85 and 102	4433
104	11 and 67 and 85 and 102	865
105	46 and 67 and 85 and 102	4231
106	103 or 104 or 105	5462
107	limit 106 to embase	4043

Sociological Abstracts 1952 – current, ProQuest (searched 9 February 2014)

ALL(vaccination or vaccine or vaccines or immunization)

AND

ALL(child* or infant* or newborn or neonat* or baby or babies or kid or kids or toddler* or mother* or woman or women or female)

LILACS, Virtual Health Library (VHL) (searched 9 February 2014)

(immunization or inmunizacion or imunizacao or vaccination or vacunacion or vacinacao or vaccine or vaccines or vacuna or vacunas or vacina or vacinas) AND (tetanus or tetanico or diphtheria or difterico or pertussis or "whooping cough" or tosferina or "tosferina" or "tosconvulsa" or "tosseconvulsa" or coqueluche or measles or sarampion or sarampo or mumps or paperas or caxumba or rubella or rubeola or mmr or polio* or tubercul* or "mycobacterium bovis" or bcg or calmette* or hepatitis or hepatite or haemophilus) AND (child or children or infant or infants or newborn or neonat* or baby or babies or kid or kids or toddler* or nino or ninos or crianca or criancas or lactante* or lactente* or "reciennacido" or "reciennacidos" or "recemnascido" or "recemnascidos") AND (randomi* or randomly or azar or acaso or control* or intervention* or evaluat* or effect* or impact or impacts or intervencion* or intervencao* or evaluar or evaluacion or avaliacao or efecto or efectos or efeito or efeitos or impacto or impactos or "serie de tiempo" or "series de tiempo" or "serie de tempo" or "series de tempo" or "serie temporal" or "series temporal" or "serietemporales" or "series temporales" or "serietemporais" or "series temporais" or "puntos de tiempo" or "pontos de tiempo" or "puntos de tempo" or "puntos de tempo" or "puntostemporales" or "pontostemporales" or "puntotemporais" or "pontotemporais" or "medidarepetida" or "medidarepetidas" or "medidasrepetida" or "medidasrepetidas" or "medicionrepetida" or "medicionrepetidas" or "medicionesrepetida" or "medicionesrepetidas")

Global Index Medicus, WHO (www.globalindexmedicus.net/) (searched 11 July 2022)

No.	Search terms	Results
	Two independent strategies
	1.
	"childhood immunisation" OR "childhood immunization" OR "childhood vaccination" OR "child immunisation" OR "child immunization" OR "child vaccination" OR "infant immunisation" OR "infant immunization" OR "infant vaccination" [in Title, Abstract, Subject]
	AND
	randomis* OR randomiz* OR trial or impact OR effect OR evaluat* OR intervention* OR "control group" OR "control groups" OR "before and after" OR "time series" OR "repeated measures" OR "repeated measurements" [in Title, Abstract, Subject]
	2.
	"immunisation coverage" OR "immunization coverage" OR "vaccination coverage" OR "vaccine coverage" [in Title, Abstract, Subject]
	AND
	child OR children OR childhood OR infant OR infants OR newborn OR "new born" OR woman OR women OR mother OR mothers [in Title, Abstract, Subject]
	AND
	randomis* OR randomiz* OR trial or impact OR effect OR evaluat* OR intervention* OR "control group" OR "control groups" OR "before and after" OR "time series" OR "repeated measures" OR "repeated measurements" [in Title, Abstract, Subject]

International Clinical Trial Registry Platform (ICTRP), WHO (searched 11 July 2022)

International Clinical Trials Registry Platform (ICTRP), Word Health Organization (WHO) (www.who.int/ictrp/en/) (searched 11 July 2022)
Five separate search strategies; 1‐4 using Advanced search, 5 using Basic search, limited to Recruitment status: All
1	(immunization coverage OR immunisation coverage OR vaccination coverage) AND (child OR children OR childhood OR infant OR infants) in the Title
2	(immunization coverage OR immunisation coverage OR vaccination coverage) AND (child OR children OR childhood OR infant OR infants) in the Condition
3	(childhood immunisation OR childhood immunization OR childhood vaccination OR child immunisation OR child immunization OR child vaccination OR infant immunisation OR infant immunization OR infant vaccination) AND (coverage) in the Title
4	(childhood immunisation OR childhood immunization OR childhood vaccination OR child immunisation OR child immunization OR child vaccination OR infant immunisation OR infant immunization OR infant vaccination) AND (coverage) in the Condition
5	(child OR children OR childhood OR infant OR infants) AND (immunization OR immunisation OR vaccination) AND (coverage)

ClinicalTrials.gov, NIH (searched 11 July 2022)

Two separate search strings ‐ Advanced search ‐ Search field: Outcome Measure ‐ Limited to: Interventional Studies (Clinical Trials)

1. "immunization coverage" OR "immunisation coverage" OR "vaccination coverage"

2. "childhood immunisation" OR "childhood immunization" OR "childhood vaccination" OR "child immunisation" OR "child immunization" OR "child vaccination" OR "infant immunisation" OR "infant immunization" OR "infant vaccination"

Data and analyses

Comparison 1. Health education.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Reception of DTP3 by 1 year of age	6	4375	Risk Ratio (IV, Random, 95% CI)	1.36 [1.15, 1.62]
1.1.1 Facility‐based health education	3	2355	Risk Ratio (IV, Random, 95% CI)	1.21 [1.01, 1.46]
1.1.2 Community‐based health education	3	2020	Risk Ratio (IV, Random, 95% CI)	1.55 [1.27, 1.88]
1.2 Uptake of BCG vaccine	2	1557	Risk Ratio (IV, Random, 95% CI)	0.99 [0.96, 1.01]
1.3 Uptake of OPV3 vaccine	1	851	Risk Ratio (IV, Random, 95% CI)	1.08 [1.04, 1.11]
1.4 Uptake of HBV3 vaccine	1	851	Risk Ratio (IV, Random, 95% CI)	1.07 [1.03, 1.10]
1.5 Uptake of BCG + DTP3 + OPV vaccines	1		Risk Ratio (IV, Random, 95% CI)	Totals not selected
1.6 Uptake of measles vaccine	4	3343	Risk Ratio (IV, Random, 95% CI)	1.25 [1.06, 1.47]
1.6.1 Facility‐based education	1	851	Risk Ratio (IV, Random, 95% CI)	1.04 [1.02, 1.07]
1.6.2 Community‐based education	3	2492	Risk Ratio (IV, Random, 95% CI)	1.38 [1.12, 1.70]
1.7 Uptake of at least 1 vaccine	1	228	Risk Ratio (IV, Random, 95% CI)	1.58 [1.21, 2.05]
1.8 Reception of all recommended vaccines by 2 years of age	3	2387	Risk Ratio (IV, Random, 95% CI)	1.24 [1.06, 1.44]

Comparison 2. Monetary incentive.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Uptake of BCG vaccine	1		Risk Ratio (IV, Random, 95% CI)	Totals not selected
2.2 Uptake of measles/MMR vaccine	2		Risk Ratio (IV, Random, 95% CI)	Subtotals only
2.2.1 Household monetary incentive	2	2709	Risk Ratio (IV, Random, 95% CI)	1.06 [0.93, 1.21]
2.2.2 Service‐level monetary incentive	1	615	Risk Ratio (IV, Random, 95% CI)	1.06 [0.95, 1.18]
2.2.3 Household + service‐level monetary incentive	1	456	Risk Ratio (IV, Random, 95% CI)	1.09 [0.96, 1.24]
2.3 Under 5 years of age fully immunised with all scheduled vaccine	2	1000	Risk Ratio (IV, Random, 95% CI)	1.05 [0.92, 1.20]

Comparison 3. Home‐based record.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Uptake of DTP3 vaccine	3		Risk Ratio (IV, Random, 95% CI)	Subtotals only
3.1.1 Home‐based record only	3	4019	Risk Ratio (IV, Random, 95% CI)	1.36 [1.06, 1.75]
3.1.2 HBR + health education	2	1502	Risk Ratio (IV, Random, 95% CI)	1.49 [1.22, 1.82]
3.1.3 HBR + sticker	1	2182	Risk Ratio (IV, Random, 95% CI)	1.46 [1.02, 2.09]

Comparison 4. Digital register.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Uptake of DTP3 vaccine	2	328	Risk Ratio (IV, Random, 95% CI)	0.98 [0.89, 1.09]
4.2 Reception of all recommended vaccines by 2 years of age	1		Risk Ratio (IV, Random, 95% CI)	Totals not selected
4.3 Uptake of BCG vaccine	1	205	Risk Ratio (IV, Random, 95% CI)	0.98 [0.92, 1.04]
4.4 Uptake of OPV3 vaccine	1	205	Risk Ratio (IV, Random, 95% CI)	1.06 [0.97, 1.17]
4.5 Uptake of HBV3 vaccine	1	205	Risk Ratio (IV, Random, 95% CI)	0.98 [0.89, 1.07]
4.6 Uptake of measles vaccine	1	205	Risk Ratio (IV, Random, 95% CI)	1.06 [0.97, 1.17]

Comparison 5. Phone call/SMS.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
5.1 Reception of DTP3/Penta 3 by 2 years of age	6	3869	Risk Ratio (IV, Random, 95% CI)	1.12 [1.00, 1.25]
5.1.1 Urban	3	1204	Risk Ratio (IV, Random, 95% CI)	1.16 [0.99, 1.35]
5.1.2 Rural	2	1069	Risk Ratio (IV, Random, 95% CI)	0.99 [0.96, 1.03]
5.1.3 Urban + rural	1	1596	Risk Ratio (IV, Random, 95% CI)	1.27 [1.19, 1.37]
5.2 Uptake of DTP3 (SMS + monetary incentive intervention)	1	766	Risk Ratio (IV, Random, 95% CI)	1.01 [0.98, 1.03]
5.3 Reception of all recommended vaccines by 2 years of age	5		Risk Ratio (IV, Random, 95% CI)	Subtotals only
5.3.1 Phone call/SMS only	5	10414	Risk Ratio (IV, Random, 95% CI)	1.06 [0.99, 1.12]
5.3.2 SMS + monetary incentive	1	766	Risk Ratio (IV, Random, 95% CI)	1.09 [1.02, 1.16]
5.4 Uptake of BCG vaccine	2		Risk Ratio (IV, Random, 95% CI)	Totals not selected
5.4.1 Phone call/SMS only	2		Risk Ratio (IV, Random, 95% CI)	Totals not selected
5.4.2 SMS + monetary incentive	1		Risk Ratio (IV, Random, 95% CI)	Totals not selected
5.5 Uptake of OPV3 vaccine	2		Risk Ratio (IV, Random, 95% CI)	Subtotals only
5.5.1 Phone call/SMS only	2	1069	Risk Ratio (IV, Random, 95% CI)	0.99 [0.94, 1.05]
5.5.2 SMS + monetary incentive	1	766	Risk Ratio (IV, Random, 95% CI)	1.01 [0.99, 1.04]
5.6 Uptake of measles vaccine	2		Risk Ratio (IV, Random, 95% CI)	Subtotals only
5.6.1 Phone call/SMS only	1	2230	Risk Ratio (IV, Random, 95% CI)	2.06 [1.64, 2.60]
5.6.2 Phone call/SMS + monetary incentive	1	766	Risk Ratio (IV, Random, 95% CI)	1.07 [1.01, 1.14]
5.7 Uptake of yellow fever vaccine	1		Risk Ratio (IV, Random, 95% CI)	Totals not selected

5.7. Analysis.

Comparison 5: Phone call/SMS, Outcome 7: Uptake of yellow fever vaccine

Comparison 6. Wearable reminder.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
6.1 Reception of DTP3/Penta 3 vaccine by 2 years of age	2	1567	Risk Ratio (IV, Random, 95% CI)	1.02 [0.97, 1.07]
6.2 Uptake of BCG vaccine	1	1382	Risk Ratio (IV, Random, 95% CI)	0.84 [0.74, 0.94]
6.3 Uptake of measles vaccine	1	1440	Risk Ratio (IV, Random, 95% CI)	1.04 [0.97, 1.12]

Comparison 7. Training of health providers ‐ IPC.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
7.1 Uptake of all recommended vaccines by 2 years of age	1	420	Risk Ratio (IV, Random, 95% CI)	5.65 [3.62, 8.83]

Comparison 8. Home visit.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
8.1 Uptake of all recommended vaccines by 2 years of age	1	419	Risk Ratio (IV, Random, 95% CI)	1.29 [1.15, 1.45]
8.2 Uptake of OPV3 vaccine	1	419	Risk Ratio (IV, Random, 95% CI)	1.22 [1.10, 1.35]
8.3 Uptake of measles vaccine	1	419	Risk Ratio (IV, Random, 95% CI)	1.26 [1.14, 1.39]

Comparison 9. Immunisation outreach.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
9.1 Reception of DTP3 by 1 year of age	1	541	Risk Ratio (IV, Random, 95% CI)	1.32 [1.11, 1.56]
9.2 Uptake of all recommended vaccines by 2 years of age	1	309	Risk Ratio (IV, Random, 95% CI)	1.33 [1.00, 1.76]
9.3 Uptake of BCG vaccine	1	647	Risk Ratio (IV, Random, 95% CI)	1.06 [0.99, 1.13]
9.4 Uptake of HBV3 vaccine	1	541	Risk Ratio (IV, Random, 95% CI)	1.36 [1.13, 1.64]
9.5 Uptake of OPV3 vaccine	1	541	Risk Ratio (IV, Random, 95% CI)	1.38 [1.16, 1.65]
9.6 Uptake of measles vaccine	1	647	Risk Ratio (IV, Random, 95% CI)	1.26 [0.91, 1.74]
9.7 Under 5 years of age fully immunised with all scheduled vaccines	2		Risk Ratio (IV, Random, 95% CI)	Subtotals only
9.7.1 Outreach only	1	1239	Risk Ratio (IV, Random, 95% CI)	3.09 [2.11, 4.53]
9.7.2 Outreach + Health Education	1	49444	Risk Ratio (IV, Random, 95% CI)	1.28 [1.23, 1.33]
9.7.3 Outreach + incentive	1	1242	Risk Ratio (IV, Random, 95% CI)	6.66 [4.78, 9.28]

Comparison 10. Integration of immunisation with other health services.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
10.1 Reception of DTP3/Penta 3 by 1 year of age	1	2192	Risk Ratio (IV, Random, 95% CI)	1.27 [1.17, 1.38]
10.2 Uptake of all recommended vaccines by 2 years of age	1	1700	Risk Ratio (IV, Random, 95% CI)	1.29 [1.16, 1.44]
10.3 Uptake of BCG vaccine	1	2089	Risk Ratio (IV, Random, 95% CI)	0.97 [0.93, 1.01]
10.4 Uptake of measles vaccine	1	1370	Risk Ratio (IV, Random, 95% CI)	1.13 [1.04, 1.22]
10.5 Uptake of yellow fever vaccine	1	1383	Risk Ratio (IV, Random, 95% CI)	1.13 [1.04, 1.22]

Comparison 11. Engagement of community leaders.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
11.1 Reception of DTP3/Penta 3 vaccine by 1 year of age	1	2020	Risk Ratio (IV, Random, 95% CI)	1.37 [1.11, 1.69]
11.2 Uptake of measles vaccine	1	1227	Risk Ratio (IV, Random, 95% CI)	1.96 [1.61, 2.39]

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Amare 2021.

Study characteristics
Methods	Non‐randomised controlled trial
Participants	Health workers
Interventions	Intervention: training supervisors on supportive supervision and mentoring based on updating supervisors on current policies, new immunisation practices, techniques, and management skills Control: not stated
Outcomes	Polio 3, Penta 3, Penta 3 dropout, and full vaccination
Duration of intervention	6 months
Notes	Funding: this work was supported by the Bill and Melinda Gates Foundation (Grant number OPP1191298).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	The study employed a pre‐post quasi‐experimental design
Allocation concealment (selection bias)	High risk	Not stated, probably not done
Blinding (performance bias and detection bias) All outcomes	Low risk	Probably done; the data were collected by 6 independent data collectors in the pre‐implementation and postimplementation phase of the study
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition not related to the interventions."30 health facilities were included from the 100 health facilities in the two districts. 15 (50%) were from Wogera district receiving the intervention and 15 (50%) were from Dabat district as the control group. Finally a total of 28 facilities (13 from the intervention group and 15 from the control group) were included for analysis. Two health facilities (one health center and one health post) were excluded from the intervention group due to security reasons."
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	High risk	Pre‐post results for the control arm not reported
Baseline outcome measurements similar?	Unclear risk	Not presented for the control arm
Baseline characteristics similar?	Unclear risk	Not presented for the control arm
Adequate protection against contamination?	Unclear risk	Insufficient information

Andersson 2009.

Study characteristics
Methods	Cluster‐RCT in Pakistan
Participants	Setting: Lasbela, one of the poorest districts in Balochistan Province in Pakistan Aim: authors hypothesised that if the community accessed information on the cost‐benefits of immunisation, the uptake of vaccines would improve without requiring improvement in service delivery Participants: 180 community groups with each group having 8 to 10 participants, both male and female. Outcome measured in children aged 12 to 23 months; 911 children at pre‐intervention and 956 at post‐intervention
Interventions	Intervention:evidence‐based discussion on immunisation in 18 clusters: trusted members of the committee were selected for a 3‐phased discussion. 9 field teams (facilitators) had discussion with 180 community groups of 8 to 10 members each in 94 villages for the intervention group. 3 phases of discussion were held with the community groups. In the first phase, the community groups discussed the situation of child immunisation in the union council, the smallest unit of the local government system. Facilitators discussed the risk of non‐vaccination for measles with the community groups. In the second phase, they discussed the cost‐benefits of vaccination and treatment of measles. The third stage featured discussion on the challenges of immunisation and identification of barriers and plans of action to increase access to immunisation services and means of spreading the discussion on vaccination. Control: usual care in 14 clusters
Outcomes	Proportion of 12‐ to 23‐month olds who had received measles vaccination Proportion of 12‐ to 23‐month olds who had received full course of DPT
Duration of intervention	August 2006 to May 2007 (9 months)
Notes	Follow‐up after 1 year (baseline conducted in spring 2005; follow‐up spring 2007) Funding: this work was carried out with the aid of a grant from the International Development Research Centre (IDRC), Ottawa, Canada, as part of the Canadian International Immunization Initiative Phase 2 (CIII2).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number generator allocated baseline communities to 18 intervention enumeration areas and 14 control enumeration areas
Allocation concealment (selection bias)	Low risk	Sequence concealed and intervention assigned centrally
Blinding (performance bias and detection bias) All outcomes	Low risk	Interviewers did not know which clusters had received the intervention, only the field co‐ordinator knew
Incomplete outcome data (attrition bias) All outcomes	Low risk	Sampling for baseline and post‐intervention surveys were done independently.
Selective reporting (reporting bias)	High risk	Not all outcomes were reported on
Other bias	High risk	The unit of study was enumeration area, analysis done at participant level; no adjustment for cluster effect. In addition, use of mothers' recall for immunisation uptake may underestimate vaccine coverage. Secondly, it is stated that "The baseline survey contacted 538 children aged 12‐23 months in intervention and 373 in control communities. The follow‐up survey contacted 536 in intervention and 420 in control communities." Increasing the number of participants in the control group at end‐line may introduce bias.
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	Baseline characteristics similar except, "mothers willing to travel to vaccinate", which was higher in the intervention than the control group
Adequate protection against contamination?	Unclear risk	Measure to prevent contamination not stated

Banerjee 2010.

Study characteristics
Methods	Cluster‐RCT in India
Participants	Setting: disadvantaged rural community in Udiapur, India with 2% immunisation coverage Participants: 1640 children aged 0 to 6 months at baseline or 1 to 3 years at the endpoint survey
Interventions	Intervention A: once‐monthly reliable immunisation camp without incentive (379 children from 30 villages at endpoint). Intervention focused on establishing regular availability of immunisation services. Consisted of a mobile immunisation team, including a nurse and assistant, who conducted monthly immunisation camps in the villages. Camp held on a fixed date every month at a fixed time (11 am to 2 pm). Presence of nurse and assistant verified by requirement of timed and dated pictures of them in the villages and by regular monitoring. Intervention B: once‐monthly reliable immunisation camp with small incentives consisting of raw lentils and metal plates for completion of schedule (382 children from 30 villages at endpoint). Intervention used the same infrastructure as intervention A, but in addition offered parents 1 kg of raw lentils per immunisation administered and a set of "thalis" (metal plates used for meals) on completion of a child's full immunisation. Value of the lentils about USD 1, equivalent to three‐quarters of 1 day's wage, and the value of the "thalis" about USD 2. Control: no intervention (860 children in 74 villages at endpoint)
Outcomes	Probability of receiving at least 1 immunisation (excluding OPV, which almost all children received) Presence of the BCG scar Number of immunisations received Probability of being fully immunised. A fully immunised child received all the vaccines in the EPI schedule (1 dose of BCG, 3 doses of DTP, 3 doses of OPV, and 1 dose of measles vaccine) by the age of 1 year
Duration of intervention	18 months
Notes	Study conducted in rural state of Rajasthan, India Funding: this study was funded by the MacArthur Foundation. All researchers declare that the research was entirely independent from the funders. The funders had no involvement in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. The intervention was funded by the Evangelischer Entwicklungdienst (Germany), InterChurch Cooperation for Development Cooperation (Netherlands), and Plan International, through Seva Mandir comprehensive plan. None of the funding organisations participated in the design of the study (although the MacArthur Foundation reviewed the design before making the funding decision), the data collection or analysis, or the decision to submit the paper for publication.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Used computer‐generated random numbers
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	"The allocation of villages to treatment or control was not blind... Surveys were undertaken in randomly selected households at baseline and about 18 months after the interventions started (end point)... Interviewers did not know which villages belonged to which intervention (or control) group"
Incomplete outcome data (attrition bias) All outcomes	Low risk	The proportion lost to follow‐up was similar across groups, due to similar reasons (household moved, unable to find child). Households lost between baseline and endpoint: 16% (71/453) in intervention A group, 17% (72/481) in intervention B group, and 17% (210/1224) in control group; 17% (363/2158) overall.
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Low risk	"Villages from all three treatment groups were sufficiently far from each other (over 20 km) so we expected no contamination between the villages"

Bangure 2015.

Study characteristics
Methods	RCT
Participants	Mother/caregiver in Kadoma City, an urban area located in the Mashonaland province of Zimbabwe
Interventions	Intervention: "In the intervention group, the mother or caregivers received the routine health education and also received automatic messages indicating the next appointment date on three occasions". Control: "In the non intervention group, the mothers or caregivers received the routine health education and were informed about their next scheduled visit."
Outcomes	“The primary outcome measure was receipt of scheduled vaccines at 6, 10 and 14 weeks. The secondary outcome measures were; delay in immunization appointment, age of child when immunized, costs, and willingness to receive SMS.”
Duration of intervention	8 months
Notes	Funding: the lead author acknowledges the financial and technical support from the Centre for Disease Control and Prevention, Zimbabwe
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“…study participants were assigned by computer generated random numbers to 1 of 2 groups: …”
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	There was no participant lost to follow‐up in either treatment group.
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Unclear risk	Baseline outcome measures not reported
Baseline characteristics similar?	Low risk	“In this study there was no significant difference in the baseline demographic characteristic of those in the intervention and control groups.”
Adequate protection against contamination?	Unclear risk	Not stated

Barham 2005.

Study characteristics
Methods	Cluster‐RCT in Mexico
Participants	Setting: Nicaragua, Mexico with immunisation rate > 90% Participants: villages with immunisation rates less than 90%
Interventions	Intervention: 2 cash transfers every 2 months; 1 general and 1 depending on school attendance Nutrition component: food supplements for children aged 4 to 23 months, under‐weight children aged 2 to 4 years, and pregnant and lactating women in beneficiary households Health component: regular healthcare appointments in health centres for the whole family Education component Control: usual care
Outcomes	Immunisation full coverage of children aged 12 to 23 months with 3 doses of DPT, BCG, and measles vaccines
Duration of intervention	12 to 35 months
Notes	The controls should originally have acted as controls for 2 years, but for political reasons, intervention in control communities occurred in late 1999, so only 18 months of comparison was possible and the control communities were, therefore, considered as cross‐over intervention communities after 1 year of observation. Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described; allocation to study arms was done at the start of the study
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding (performance bias and detection bias) All outcomes	High risk	Study was not blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Unclear risk	Not stated
Baseline outcome measurements similar?	High risk	Baseline level of vaccination rate lower in treatment group
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Unclear risk	Protection against contamination not stated

Basheer 2021.

Study characteristics
Methods	Cluster non‐RCT
Participants	Health workers
Interventions	Intervention: training of PHC workers on interpersonal communication. The IPC skills were applied during immunisation sessions via direct communication with the mothers at fixed or outreach sessions and house‐to‐house visits for tracking missed opportunities. Control: routine care
Outcomes	Full, partial, and non‐immunisation
Duration of intervention	2.5 days with each session lasting 3 hours
Notes	Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quasi‐experimental design
Allocation concealment (selection bias)	Unclear risk	Not described, probably not done
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	No participant lost to follow‐up in either treatment group.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Low risk	Baseline outcomes were similar.
Baseline characteristics similar?	Low risk	Baseline characteristics were similar.
Adequate protection against contamination?	Unclear risk	Not stated

Basinga 2011.

Study characteristics
Methods	Cluster‐RCT in Rwanda
Participants	Healthcare providers
Interventions	Performance‐based payment of healthcare providers (payment for performance; P4P) versus traditional input‐based funding
Outcomes	Immunisation, prenatal care visits and institutional deliveries, quality of prenatal care, and child preventive care visits
Duration of intervention	18 to 23 months
Notes	Funding: World Bank’s Bank‐Netherlands Partnership Program and Spanish Impact Evaluation Fund, the British Economic and Social Research Council, Government of Rwanda, and Global Development Network. The sponsors of the study had no role in data analysis, data interpretation, or writing of the report. All authors had full access to all data in the study and take responsibility for the integrity of the data and the accuracy of data analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was done by coin toss. "Administrative districts with pre‐existing P4P schemes managed by non‐governmental organisations were excluded from this assessment. The remaining districts were then grouped into eight blocks based on rainfall, population density, and livelihood data from the 2002 Census. Blocks covered between two and four districts, depending on district characteristics and size. The blocks were then divided into two sides, and one side of each block was randomly assigned to either the intervention or control group."
Allocation concealment (selection bias)	High risk	The unit of allocation was institution (health facilities), however "Rollout of the scheme was staggered for this assessment were available for between 23 months and 18 months of exposure, according to when a specific facility was switched to P4P‐based funding."
Blinding (performance bias and detection bias) All outcomes	Low risk	“All surveys were done by trained enumerators hired by external firms specialised in data collection who were masked to whether they were interviewing in an intervention or control area”
Incomplete outcome data (attrition bias) All outcomes	Low risk	"The rate of attrition in the number of households available for a second interview was not statistically different between the treatment group (11·8%) and control group (12.1%)."
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	"Just before implementation of the baseline survey, the administrative district boundaries were redefined by the government in a decentralisation process.16 As a result, some of the districts selected for our assessment were combined with districts that already had the exisitng P4P schemes. Because P4P schemes could not be removed from health facilities in which they had already been implemented, and because P4P was managed at the district level, the government enrolled all facilities in newly formed districts that had existing P4P schemes into the first phase of the rollout. As a result of this district reorganisation, we had to switch the assignment (intervention or control) for eight districts from four blocks, and add one block to the sample. In the end, the study’s nine blocks included 19 districts in total, of which 12 were assigned to the treatment group and 7 were assigned to the comparison group."
Baseline outcome measurements similar?	Low risk	"No difference was recorded in the probability that a child aged 12–23 months was fully immunised"
Baseline characteristics similar?	Low risk	"Baseline characteristics were not statistically different between facilities in the intervention group and facilities in the control group"
Adequate protection against contamination?	Unclear risk	Not information

Bolam 1998.

Study characteristics
Methods	RCT in Nepal
Participants	Setting: main maternity hospital in Kathmandu, Nepal Aim: tested the effectiveness of 1‐to‐1 health education with perinatal mothers in a hospital setting in Nepal on infant care and family planning Participants: 540 post‐partum women
Interventions	Intervention A: 20‐minute, 1‐to‐1 health education immediately after birth and 3 months later Intervention B: 20‐minute, 1‐to‐1 health education at birth only Intervention C: 20‐minute, 1‐to‐1 health education at 3 months only Intervention D: control (no individual health education)
Outcomes	Duration of exclusive breastfeeding Appropriate immunisation of infant Knowledge of oral rehydration solution and need to continue breastfeeding during diarrhoea Knowledge of infant signs suggesting pneumonia Uptake of postnatal family planning
Duration of intervention	20‐minute, individual health education at birth and 3 months later Outcomes assessed at 3 and 6 months
Notes	First education session conducted in quiet room before discharge from hospital. Second education session conducted in the mothers' home 3 months after delivery. Although the health education given at birth and 3 months covered broadly the same areas, more emphasis was placed on the importance of exclusive breastfeeding in the first session and on the need for family planning in the second session. Topics covered were infant feeding, treatment of diarrhoea, recognition of and response to symptoms suggesting acute respiratory infection in young infants, importance of immunisation, and importance of contraception after the puerperium. At the end of each session, the health educator repeated the key messages covered and asked the mother if she had any other questions. Funding: research grant from the UK Department for International Development
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The unit of randomisation was the individual mother. Restricted randomisation was used in blocks of 20, each block consisting of a random ordering of the numbers 0‐19. Numbers 0‐4, 5‐9, 10‐14, and 15‐19 were assigned to groups A to D respectively"
Allocation concealment (selection bias)	Low risk	"Timing of assignment was when a mother was identified by the research team either in labour or shortly after delivery. The details of allocation to groups for consecutively recruited mothers were in sealed envelopes... The generator of the assignment was not involved in the execution of the allocation"
Blinding (performance bias and detection bias) All outcomes	Low risk	"The mothers recruited and the health educators were not blind to the assignment of mothers to different groups. The outcome assessors were always blind to the assignment at both the 3 and 6 month follow up visits. Staff who were involved in data collection at the 3 month follow up were not involved in data collection at 6 months."
Incomplete outcome data (attrition bias) All outcomes	High risk	Each of the 4 groups (A to D) had 135 women. At 6 months, the percentage of women lost to follow‐up was 29% in group A, 21% in B, 26% in C, and 24% in D. No explanation is given for the attrition.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	None suspected
Baseline outcome measurements similar?	Unclear risk	Not stated
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Low risk	Yes

Brugha 1996.

Study characteristics
Methods	Matched and cluster RCT in Ghana
Participants	Setting: urban settings in Ghana with regular immunisation services Aim: addressing low immunisation coverage in spite of developed immunisation infrastructure Participants: children aged 12 to 18 months; included 200 mother‐and‐child pairs in the intervention group and 219 in the control group
Interventions	Intervention: home visits in 30 clusters. During home visits, interviewers (university students) administered questionnaires to mothers or female caregivers and fathers or male caregivers of children aged 12 to 18 months. Immunisations recorded from road‐to‐health card or clinic record (if card was missing) in a register. All respondents were advised to bring identified children who had not completed the immunisation schedule to the clinic for immunisation. A referral note was given to each child to bring to the clinic. Children who failed to complete immunisation were identified from the register and a maximum of 3 home visits made to each child within 6 months. Control: standard care in 30 clusters
Outcomes	Completion of polio1, OPV3, and measles Completion of schedule
Duration of intervention	6 months
Notes	6 months of follow‐up Funding: data collection in the Eastern Region of Ghana was partially funded by the Save the Children Fund (Ghana).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"... each pair of clusters was randomly chosen for the survey..." Not described
Allocation concealment (selection bias)	Unclear risk	Not described, probably not done
Blinding (performance bias and detection bias) All outcomes	High risk	Neither the provider nor the child was blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants were accounted for.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Children in registered and unregistered houses were included in the intervention group, but only children in registered houses were included in the control group.
Baseline outcome measurements similar?	Low risk	Baseline immunisation coverage in the 2 groups was not statistically significant.
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Low risk	"Contiguous clusters were paired, as far as possible within enumeration areas, and one of each pair of clusters was randomly chosen for the survey and home intervention"

Chen 2016.

Study characteristics
Methods	Matched cluster‐randomised controlled trial
Participants	Setting: Xiaba and Nanba, Sichuan province, China Participants: village doctors
Interventions	Intervention: "In the intervention group, we gave a mobile phone with the EPI app to village doctors to manage child vaccination and we used text messages to alert caregivers about upcoming vaccinations. The EPI app had four modules with distinct functions: 1) making appointments; 2) recording vaccination status; 3) tracking overdue children; and 4) providing education." Control: “In the control group, village doctors conducted their vaccination work in their usual way and text messages were also implemented to alert caregivers about upcoming vaccinations. This was a change from our protocol because when we designed the study, the text message component was not included into the protocol.”
Outcomes	“The primary outcome was full vaccination coverage, defined as the percentage of surveyed children aged 12‐23 months immunized with three doses of Hepatitis B, one dose of BCG, three doses of OPV, three doses of DPT and one dose of measles vaccine before their first birthday. The secondary outcomes were vaccination coverage indicators of one dose BCG, three doses of Hepatitis B, three doses of OPV, three doses of DPT, one dose of MV.”
Duration of intervention	2 years
Notes	Funding: the study was funded by Save the Children, China
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“We chose the block Tools package in the software program “R” (https://www.r‐project.org/) for matching and randomization. We created a measure between pairs of villages from several continuous variables (as we used the previously mentioned three variables). We set an allowable range of differences between pairs of villages on one variable and then randomly assigned paired villages to intervention or control groups.”
Allocation concealment (selection bias)	Low risk	The unit of allocation was professionals (village doctors) and allocation was at the start of the study. Also, "after a bio‐statistician generated the random allocation, the random allocation was sent to the program manager at Save the Children, Sichuan Office, who installed the smartphone with EPI app and distributed this to village doctors in the intervention group."
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Doctors were the unit of randomisation, and all 32 doctors (16 doctors per group) completed the study.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Violation of study protocol. "In the control group, village doctors conducted their vaccination work in their usual way and text messages were also implemented to alert caregivers about upcoming vaccinations. This was a change from our protocol because when we designed the study, the text message component was not included in the protocol."
Baseline outcome measurements similar?	Low risk	Baseline outcome measures were similar between the intervention and control group.
Baseline characteristics similar?	Low risk	Baseline characteristics were similar.
Adequate protection against contamination?	Unclear risk	Inadequate information to make a judgement

Dicko 2011.

Study characteristics
Methods	Cluster‐RCT in Mali
Participants	Setting: Kolokani, a district in Mali hyperendemic for malaria and with immunisation level < 50% Participants: children aged 0 to 23 months
Interventions	Intervention: intermittent preventive treatment of malaria in infants (in 11 clusters), i.e. administration to infants of ½ tablet of sulphadoxine‐pyrimethamine along with EPI vaccines (DTP2, DTP3, and measles/yellow fever vaccine). Community leaders were sensitised and health staff were trained. Supports for child health interventions were modified to allow the recording of the administration of the sulphadoxine‐pyrimethamine along with EPI vaccines and the health interventions. Control: standard care in 11 clusters
Outcomes	Proportion of 9‐ to 23‐month old children completely immunised with BCG, 3 doses of DTP, 1 dose of measles, and yellow fever vaccines
Duration of intervention	12 months
Notes	Study conducted from December 2006 to December 2007. Sample size for the baseline survey estimated using the following assumptions. Based on a precision of 6% and alpha error of 5% and DTP3 coverage of two‐thirds (67%), a sample of 472 children was selected using a cluster effect of 2. This sample size was doubled to take into account analysis for specific age categories and increased by 10% to take into account missing information, making a total sample size of 1050 children aged 0 to 23 months. Funding: the study was funded by the Bill and Melinda Gates Foundation to UNICEF in support of the IPTi Consortium (http://www.ipti‐malaria.org).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The study was an open cluster‐randomised trial. The 22 health areas (sub‐districts) of the district of Kolokani were randomised in a 1:1 ratio. The health areas were numbered from 1 to 22 and each number was written on a piece of paper that was folded. The 22 pieces of paper were then mixed and placed in a box and 11 of them were randomly drawn to serve as intervention.
Allocation concealment (selection bias)	High risk	The pieces of paper were randomly drawn to serve as intervention and control by one of the trainees in the presence of the representatives of the 22 communities’ health centres.
Blinding (performance bias and detection bias) All outcomes	High risk	Study was an open, cluster‐randomised trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	There was no significant attrition amongst the groups. The same participants that were surveyed at baseline were surveyed at post‐intervention.
Selective reporting (reporting bias)	High risk	One independent survey was taken pre‐intervention. There was no baseline survey specific for each group.
Other bias	Low risk	None
Baseline outcome measurements similar?	High risk	No data to compare the groups directly at baseline
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	High risk	Training of staff was carried out in both control and intervention communities, followed by public randomisation.

Dissieka 2019.

Study characteristics
Methods	RCT
Participants	Setting: rural, semi‐urban, and urban settings in Korhogo town, Côte d'Ivoire Participants: mothers/caregivers
Interventions	Intervention: "Mothers (or caretakers) in the intervention group were provided SMS or voice message reminders, based on their preference, prior to each scheduled facility visit and two additional reminders in the event of non‐attendance. A mobile web service platform (IvocarteR, Abidjan) was used to register the mother’s mobile phone number and child’s visit schedule. SMS and voice messages were then automatically generated and transmitted to recipients at designated times. Attendance records for each visit were transmitted directly from facility staff to study personnel via the IvocarteR platform." Control: "Mothers in the control group were not provided any SMS or voice messages and were instructed to refer to the child’s health card for appointment dates, as per the standard of care in Cote d’Ivoire."
Outcomes	“Pentavalent 1 (DPT+ Hep B + Hib) immunization at 6 weeks, pentavalent 2 at 10 weeks, pentavalent 3 at 14 weeks, vitamin A supplement at 6 months, and MMR/yellow fever immunizations at 9 months of age delivered at public sector facilities.”
Duration of intervention	1 year
Notes	Funding: none
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomisation was used to allocate mother‐child pairs into groups based on rural, semi‐rural, or urban location of the health facilities. "Randomization was performed using an automated system".
Allocation concealment (selection bias)	Low risk	“... randomization schedules were concealed from health facility personnel.”
Blinding (performance bias and detection bias) All outcomes	Low risk	"Health providers were blinded to the randomization scheme"
Incomplete outcome data (attrition bias) All outcomes	Low risk	“…immunization and VAS data were uploaded to the web server in real‐time, which enabled more efficient monitoring of each child’s progress. This likely resulted in more complete and accurate data, as compared to self‐reported data and child health cards.”
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	“In addition, as 19 out of the 29 health facilities in this study also participated in the previous pilot intervention, health providers and communities in these areas may have been more sensitized to the importance of immunization and VAS, as compared to the other 10 facilities. As health facilities were purposively selected in areas with a well‐functioning mobile phone network, the findings may not be generalizable to areas with poorer network coverage and where access to mobile phones may also be limited.”
Baseline outcome measurements similar?	Unclear risk	Baseline outcome measures not provided.
Baseline characteristics similar?	Low risk	“Participant characteristics were similar between the two groups at recruitment.”
Adequate protection against contamination?	Low risk	It is unlikely that participants in the control group received the intervention.

Djibuti 2009.

Study characteristics
Methods	Cluster‐RCT in Georgia
Participants	Setting: low immunisation coverage despite healthcare reforms. Human resource management was weak with lack of knowledge and skills in management and supervision especially at the peripheral levels. Participants: district immunisation managers, PHC providers
Interventions	Intervention: development of supportive supervision guidelines for district immunisation managers in 15 clusters: intervention consisted of development of supportive supervision guidelines and tools for district managers, training in continuous supportive supervision, monitoring, and evaluation of performance. Each district manager visited subordinated health facility at least once a month. On‐the‐job training was provided for immunisation managers to improve on supervision practices to help providers solve problems encountered in immunisation Control: no intervention in 15 control clusters
Outcomes	DTP3, polio 3, and HBV3 coverage Difference in proportion of coverage from baseline
Duration of intervention	12 months
Notes	Follow‐up study conducted after 1 year of intervention Funding: International Development Research Centre (IDRC), Ottawa, Canada, as part of the Canadian International Immunization Initiative Phase 2 (CIII2)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Stratified cluster randomisation was used to select the 30 cluster units out of the nation's 67 districts and allocate them into the two study groups (intervention and control), yielding two allocation sequences of 15 clusters each"
Allocation concealment (selection bias)	Unclear risk	Allocation was performed for all units at the start of the study.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information, probably not done
Incomplete outcome data (attrition bias) All outcomes	Low risk	All the participants were accounted for.
Selective reporting (reporting bias)	Low risk	Not suspected
Other bias	High risk	There was an increase in the number of participants post‐intervention in both arms, but the increase was more significant in the intervention arms. Also, "during the course of the intervention, the country improved healthcare financing for low‐income people and there was also improved country level economic growth thus improving access to health care. "It is possible that improved access to health care may have contributed to improved immunization coverage in Georgia".
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	Demographic and employment characteristics were similar among Center of Public Health staff respondents in the intervention and control groups, both at baseline and follow‐up, except for mean years of experience, which was more among the control group.
Adequate protection against contamination?	Low risk	"Given that immunization managers supervise health workers only within their districts, and similarly health workers provide immunization services to target population residing in communities within the same district, the risk of contamination of the control group with the intervention is negligible. Use of smaller units (e.g. village) would have posed a higher risk of contamination of intervention activities in control clusters."

Domek 2016.

Study characteristics
Methods	RCT
Participants	Setting: low‐income population, Guatemala city Participants: “Parents of infants between the ages of 8 and 14 weeks presenting for the first dose of the 3‐dose infant primary immunization series …”
Interventions	Intervention: "Those randomized into the intervention group also received … SMS text messages at six, four, and two days before the next scheduled date for visits 2 and 3". Control: usual care
Outcomes	“The primary outcomes for this study were the proportion of parents who were sent SMS messages and parental satisfaction with the intervention.”
Duration of intervention	6 months
Notes	Funding: this study was funded by a Bill and Melinda Gates Foundation Grand Challenges Explorations grant (OPP1061430) and a small operational grant from the Pan American Health Organization.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Participants were allocated to either an intervention or usual care group using a computer‐generated randomization scheme ..."
Allocation concealment (selection bias)	Low risk	Not described, probably centrally allocated. "Upon unlocking the database, it was noted that a disproportionate number of participants were randomized into the intervention group during the first month and the usual care group during the second month of the enrollment period. Equal numbers of intervention and usual care participants were enrolled at the two clinic sites"
Blinding (performance bias and detection bias) All outcomes	Low risk	Investigators were blind to the allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Intention‐to‐treat analysis was done.
Selective reporting (reporting bias)	Low risk	Not suspected
Other bias	High risk	The study was not adequately powered to evaluate efficacy. Some parents did not recall receiving text messages. Vaccination records were confirmed only in clients that returned to the study sites. Selection favoured children who were already receiving their vaccination on time. Study sites experienced intermittent shortages of pneumococcal vaccine.
Baseline outcome measurements similar?	Unclear risk	Not stated
Baseline characteristics similar?	Low risk	“Parents in the usual care group had significantly higher income with more fathers working; otherwise, there were no significant differences between the baseline demographics of intervention and usual care children and their parents”. This is likely due to chance because only 2 characteristics out of 12.
Adequate protection against contamination?	Unclear risk	Not stated

Domek 2019.

Study characteristics
Methods	RCT
Participants	Caregivers aged 18 years and above
Interventions	Intervention: "…those randomized into the intervention group would receive … text messages translated into Spanish at three, two, and one days before the next scheduled date for visits 2 and 3 … The local data manager entered each child’s name, scheduled visit date, clinic, and caregiver’s mobile number into a computer system connected to the SMS server both at enrollment and after visit 2. Automated SMS texts were generated using a customized computer‐based software program hosted by the mobile telecommunications company ClaroTM." Control: "As part of the standard of care, clinic staff also printed the next vaccination visit date in the child’s government‐issued immunization card for both intervention and usual care participants."
Outcomes	2nd dose of Penta, pneumococcal, polio, and rota and 3rd dose of Penta and polio
Duration of intervention	"All children were followed for at least eight months after enrollment."
Notes	Funding: this work was supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development at the National Institutes of Health (grant number 1R21HD084115‐01) and the Thrasher Research Fund Early Career Award Program (award number 12797). The funders had no involvement in the study design and conduct, data collection and analysis, interpretation of the data, decision to publish, or preparation of the manuscript.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"... participants were allocated to either an intervention or usual care group using a computer generated block randomization scheme (block size of 10) based on urban and rural clinic sites."
Allocation concealment (selection bias)	Unclear risk	Not described, probably not done
Blinding (performance bias and detection bias) All outcomes	Low risk	"Caregivers and study nurses were blinded to study group allocation at the initial enrollment visit. The statistician was blinded to the randomization."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Intention‐to‐treat analysis was done.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Vaccine shortages, selection bias (selecting children presenting for first visit vaccination), server error with messages delivered after the visit date.
Baseline outcome measurements similar?	Low risk	Baseline characteristics were similar.
Baseline characteristics similar?	Low risk	"There were no significant differences between the baseline demographics of intervention and usual care children and their caregivers."
Adequate protection against contamination?	Low risk	It is unlikely participants in the control group received the intervention.

Ekhaguere 2019.

Study characteristics
Methods	RCT
Participants	Setting: Ondo and Akure, Nigeria Participants: “Parturient women and their healthy newborn infants delivered at MCH‐Ondo and Akure”
Interventions	Intervention: "We developed a customised Windows software application (app) designed to send automated voice call text and email immunisation reminders. We integrated a secure cloud communications platform, called Twilio, into the app. Messaging and voice were sent by Twilio through the app. Date of birth of the newborn and the phone number of the mother and father, when provided, were inputed into the app. The immunisation reminders were auto calculated from date of birth of the child and tailored to the local immunisation schedule. ...The intervention group received the automated text and call reminder plus standard care, while the control group received only standard care" Control: “A child‐health immunisation card, which listed the ages when a child was to receive his/her immunisation, comprised standard care. ”
Outcomes	"The primary outcome was the proportion of infants who received the Penta‐1, 2 and 3 immunisations (henceforth referred to as Penta‐3) at 18 weeks of age."
Duration of intervention	2 years
Notes	Funding: the study was funded by the Thrasher Research Fund (award no. 13813). The funder of the study had no role in study design, data collection, data analysis, data interpretation or writing of the report.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Mother–infant pair were assigned to study groups in a 1:1 ratio was by a permuted randomisation scheme, using balanced random blocks of 6, 8 or 10. We stratified the randomisation by study site to account for center population differences"
Allocation concealment (selection bias)	Low risk	"Allocation assignments were stored in sealed opaque envelopes and mailed via courier to the local study principal investigators. Only after obtaining written informed consent did the local study teams know the allocation assignment."
Blinding (performance bias and detection bias) All outcomes	Low risk	“Neither study participants nor research team were blinded. However, the immunisation clinic staff (those who administered and recorded immunization) were blinded to study group allocations.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomised participants were included in the final analysis.
Selective reporting (reporting bias)	Low risk	Outcomes in the protocol were reported.
Other bias	High risk	“… the study was impacted by a hospital workers’ strike lasting 6 weeks (2February to 15 March 2017). The strike interrupted enrolment, immunisation receipt and monitoring. During this period, parents sought other government and private clinics for immunisations.”
Baseline outcome measurements similar?	Low risk	Baseline characteristics were similar.
Baseline characteristics similar?	Low risk	“Infant and maternal demographic information were similar in both groups.”
Adequate protection against contamination?	Low risk	It is unlikely that the control group participants received the intervention.

Engineer 2016.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: Afghanistan Participants: health facilities
Interventions	Intervention facilities were given bonus payments based on the MCH services provided. Control facilities provided usual care without bonuses.
Outcomes	Outcomes were contraceptive prevalence, proportion of deliveries with at least one antenatal care visit, proportion of deliveries with a skilled birth attendant, proportion of births with at least one postnatal care visit in the first 6 weeks, proportion of children aged 12 to 23 years with pentavalent 3 vaccination
Duration of intervention	2 years
Notes	Funding: this work was supported by the Government of Afghanistan Ministry of Public Health (MOPH). One of the authors was supported by the Future Health Systems Research Programme Consortium, funded by the UK’s Department for International Development (DFID).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Not described, but probably done. “All 442 BPHS health facilities were stratified … and then randomly assigned to the P4P or comparison arm.”
Allocation concealment (selection bias)	Low risk	The units of allocation were the health facilities and allocation was performed on all units at the start of the study.
Blinding (performance bias and detection bias) All outcomes	Low risk	"There was no masking of the health workers or managers due to the nature of the intervention, though the intervention was not advertised to the public." However, the "trained interviewers, who were masked to type of site, completed both surveys ..."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Independent sampling of participants done at pre‐ and post‐intervention surveys.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	None detected
Baseline outcome measurements similar?	Low risk	“The baseline surveys provided information to the MOPH about health conditions in the study area, and demonstrated that the P4P and comparison areas were similar with respect to study outcomes and demographic characteristics at the beginning of the trial.”
Baseline characteristics similar?	Low risk	See comment above.
Adequate protection against contamination?	Low risk	Catchment area was contiguous with the health facilities. It is not clear if this affected the study sites, if they were also contiguous. However, "NGOs managing facilities were contracted by the MOPH to provide services throughout a province, thereby managing both intervention and comparison sites, potentially preventing ‘contamination’ of P4P to comparison sites."

Gibson 2017.

Study characteristics
Methods	Cluster RCT
Participants	Setting: Gem and Asembo districts, Kenya Participants: caregiver of infants aged 0 to 34 days
Interventions	Intervention: "SMS reminders were sent three days and the day before scheduled immunisation visits at ages 6 weeks, 10 weeks, and 14 weeks for the three doses of pentavalent vaccine and age 9 months for measles vaccine using the free and open‐source RapidSMS platform. ... In addition to receiving SMS reminders, caregivers were sent either 75 KES (group 3) or 200 KES (group 4) to their mobile phone for each timely dose of pentavalent and measles vaccine received..." Control: usual care
Outcomes	“The primary outcome was the proportion of fully immunised children by 12 months of age, defined as receiving BCG, three doses of polio vaccine, three doses of pentavalent vaccine, and measles vaccine. … Vaccination coverage at 12 months of age and timely vaccination for pentavalent, polio, and measles vaccines were predetermined as secondary outcomes.”
Duration of intervention	1 year
Notes	Funding: Bill & Melinda Gates Foundation. The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A constrained randomisation was done with GAUSS Mathematical and Statistical System by one of the study investigators, …" “At a public randomisation ceremony on Sept 12, 2013, village chiefs determined the final randomisation outcome by picking numbered balls from a cloth sack to select one of these 1000 sequences,"
Allocation concealment (selection bias)	Unclear risk	Allocation was performed for all units at the start of the study.
Blinding (performance bias and detection bias) All outcomes	Low risk	“Due to the nature of the intervention and study design, study participants were not masked to their study group allocation". "Field staff were not informed of a village’s allocation, but this could be inferred from some enrolment and follow‐up survey questions". Not likely to affect outcome assessment.
Incomplete outcome data (attrition bias) All outcomes	High risk	Only participants that completed the studies were analysed (per protocol analyses).
Selective reporting (reporting bias)	Low risk	All relevant outcomes in the methods section were reported in the results section.
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Unclear risk	Baseline outcome measured but not provided.
Baseline characteristics similar?	Low risk	Baseline outcome measured, but not provided. The authors reported that baseline characteristics were similar.
Adequate protection against contamination?	Unclear risk	No information to support judgement

Habib 2017.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: high‐risk population in conflict‐affected and insecure settings (Bajaur, Karachi, and Kashmore) in Pakistan Participants: children aged 1 month to 5 years
Interventions	Intervention: Intervention B: received additional interventions with community outreach and mobilisation using an enhanced communication package, and provision of maternal and child health immunisation services through low‐cost health camps established to run from day 4 of polio supplementary immunisation activities Intervention C: the clusters in arm C received the same intervention package as arm B with the addition of IPV delivered at the maternal and child health immunisation strategy camps Control: Intervention A: received routine care
Outcomes	Coverage of OPV, IPV, and routine EPI vaccines and changes in the proportion of unvaccinated and fully vaccinated children between baseline and end‐line surveys
Duration of intervention	12 months
Notes	Funding: Bill & Melinda Gates Foundation. The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A computer algorithm was used to perform restricted randomisation in blocks of 20 by matching the population size, socioeconomic status, OPV coverage, and extended programme on immunisation (EPI) coverage, to assign (1:1:1) eligible clusters to three groups."
Allocation concealment (selection bias)	Unclear risk	No information.
Blinding (performance bias and detection bias) All outcomes	Low risk	Though not masked, this is assumed to be low based on the report: "an independent team conducted baseline, endline, and post‐supplementation immunisation strategy surveys at the end of each round. Because of the nature of the intervention, trial investigators were not masked. The main trial statistician was not involved in field implementation."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No incomplete data. Analysis was at the cluster level.
Selective reporting (reporting bias)	Low risk	Not suspected
Other bias	Low risk	Nil
Baseline outcome measurements similar?	Low risk	Baseline outcomes were similar
Baseline characteristics similar?	Low risk	Yes: "Baseline sociodemographic characteristics of enrolled children and their families were similar but with slightly poorer access to an improved water source in arm B."
Adequate protection against contamination?	Low risk	"To avoid potential contamination between arms, the community mobilisation teams informing communities in arms B and C about health camps also provided colour‐coded invitation cards required for visiting the health camps, and vaccine allocation (additional IPV) was made as per the colour codes."

Hu 2017.

Study characteristics
Methods	RCT
Participants	Pregnant mothers attending prenatal care in Zhejiang, China
Interventions	Intervention: "Every participant in the intervention group was administrated a 15 minutes of one‐on‐one interactive vaccination education session, which was prepared by the researchers from Zhejiang provincial CDC. The session was delivered through physicians of selected hospitals who played the role of the educator. The education session included issues on the importance of vaccination, the schedule of vaccination, immunization policy in China, immunization doses, adverse reactions, and contradictions." Control: "The participants in the control group did not receive any educational instructions."
Outcomes	Improving maternal knowledge on immunisation and the vaccination coverage of their infants
Duration of intervention	12 months
Notes	Funding: this study was supported by the general medical research program of Zhejiang province in 2014 (programme number: 2014KYA240).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Each participant was given an identification number and was randomly allocated into the intervention group or the control group through a computer generated randomization list."
Allocation concealment (selection bias)	High risk	Allocation not concealed.
Blinding (performance bias and detection bias) All outcomes	Low risk	All participants were blinded to their group assignment at recruitment and during the completion of the baseline survey. Given that it was an education intervention study, the blindness of the study team and participants through the whole study period was impossible.
Incomplete outcome data (attrition bias) All outcomes	High risk	Per protocol, analysis was done. About 32% of the participants were lost to follow‐up and no reason was provided.
Selective reporting (reporting bias)	Low risk	All relevant outcomes in the methods section were reported in the results.
Other bias	High risk	"... the follow‐up period of infants was only 12 months after delivery. A longer observation period might highlight the differences in the completeness and the timeliness of the other NIP vaccine doses. Participants could receive vaccination information from other source (e.g., Internet, television, other health personnel) during the 3 months interval between the pre‐ and the post‐surveys and it could induce bias and interfere the results.”
Baseline outcome measurements similar?	Unclear risk	Baseline outcome indicators were not reported.
Baseline characteristics similar?	Low risk	"No statistically significant difference of the demographics between the intervention and the control groups was observed"
Adequate protection against contamination?	Unclear risk	Not reported.

Kawakatsu 2020.

Study characteristics
Methods	RCT
Participants	Mothers attending clinic for either child vaccination, family planning, or antenatal care
Interventions	Intervention: "The clients in the intervention group received an SMS text reminder in English two days before the upcoming appointments... Those in the intervention group not having showed up for given appointments received an additional SMS text reminder seven days after the original appointment date as the defaulter tracing measure. The SMS text reminders were customized ..." Control: did not receive an SMS text
Outcomes	Child vaccinations
Duration of intervention	3 months
Notes	Funding: this study was conducted as a part of the Japan International Cooperation Agency (JICA) technical cooperation project ‘‘Strengthening Pro‐Poor Community Health Services in Lagos State.” JICA agreed on the study design but had no roles in data collection, analysis, or interpretation of the results. The authors had full access to all study data and had final responsibility for the decision to submit for publication.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	A 2‐arm, multi‐centred, randomised controlled trial (RCT); appointments made and pooled in the server were randomised into intervention and control arms. Method of randomisation not stated.
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Low risk	The health workers stationed at the 33 PHCs were blinded to the random assignment procedure and results. Thus, they were unable to know to which clients received SMS text reminders.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants were accounted for.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Recipient receipt of SMS could not be confirmed.
Baseline outcome measurements similar?	Unclear risk	Information not reported
Baseline characteristics similar?	Unclear risk	Information not reported
Adequate protection against contamination?	High risk	No protection against contamination.

Kazi 2018.

Study characteristics
Methods	RCT
Participants	Infants less than 2 weeks in an urban settlement in Pakistan
Interventions	Intervention: "The intervention group, in addition to this standard counselling, received 4 SMS reminders in the week that the enrolled child was due for the EPI vaccines according to the RI schedule. Four one‐way SMS text reminders according to the language preference as captured in the baseline survey were sent in the week that the child was due for EPI vaccine according to the EPI schedule." Control: received one‐time standard verbal counselling at the time of initial visit (enrolment) by the study staff regarding the timing of EPI vaccines at 6, 10, and 14 weeks
Outcomes	“The primary outcome was to compare the proportion of children immunized up to date at 18 weeks of age. The secondary outcome was to evaluate the timing of the vaccine received according to the schedule of the EPI.”
Duration of intervention	16 weeks per participant
Notes	Funding: the study was funded by the World Health Organization (EM.2O13‐IER‐RPCTSA‐OO8)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“... the randomization list was generated through computer assignments with a block of 6 children,…”
Allocation concealment (selection bias)	Low risk	Allocation sealed in opaque envelopes that were opened at the time of enrolment after informed consent.
Blinding (performance bias and detection bias) All outcomes	High risk	“... the participants could not be blinded due to overt participation and nature of the intervention.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Five children lost to follow in the intervention arm (4 died) versus 7 (2 died) in the control arm. Intention‐to‐treat analysis done.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Small sample size may have underpowered the results.
Baseline outcome measurements similar?	Unclear risk	Baseline outcome measurements not reported.
Baseline characteristics similar?	Low risk	"There was no important difference in the baseline and demographics information among intervention and control arms"
Adequate protection against contamination?	Unclear risk	Not stated

Linkins 1994.

Study characteristics
Methods	Non‐RCT
Participants	Children under 2 years in Georgia
Interventions	Prerecorded general/specific vaccination messages as a reminder or a recall using automated telephone dialling machines. Reminder calls were made a day before the vaccination due date and recall was done soon after randomisation.
Outcomes	Second and third doses of DTP, OPV, and first dose of MMR
Duration of intervention	30 days follow‐up
Notes	Funding: this study was supported in part by grant H23‐CCH404440 from the Centers for Disease Control and Prevention to the Georgia Division of Public Health.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Use of odd and even numbers for allocation of participants
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	No attrition
Selective reporting (reporting bias)	Low risk	All relevant outcomes reported.
Other bias	High risk	It was possible that messages were received by other family members using the same telephone.
Baseline outcome measurements similar?	Unclear risk	Not stated
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Unclear risk	Not stated

Maldonado 2020.

Study characteristics
Methods	Cluster‐RCT
Participants	Pregnant women who were 28 to 32 weeks gestation
Interventions	Intervention: Chamas is a group‐based, CHV‐led health education programme that supports women during the first 1000 days of their child’s life. Participants in Chamas attend 60‐ to 90‐minute sessions 2 times a month, which include discussions on health and social topics relevant to antenatal, postpartum, and early childhood experiences. Control: received standard of care (home visits)
Outcomes	Immunising infants with the oral polio vaccine within 2 weeks postpartum, immunising infants with the measles vaccine (measles I) by 12 months of age and completing the infant immunisation series per WHO and Republic of Kenya MOH standards by 12 months of age
Duration of intervention	12 months
Notes	Funding: this study was supported by Grand Challenges Canada (0755‐03).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The trial data manager used a simple random allocation sequence generated by PASS (V.11.0.10) to designate cluster assignment.
Allocation concealment (selection bias)	Low risk	The units of allocation were health facilities, and allocation was performed on all units at the start of the study.
Blinding (performance bias and detection bias) All outcomes	Low risk	"We masked data collectors (trained AMPATH research assistants), investigators and analysts to cluster allocation throughout the trial; however, both arms were identifiable to participants and CHVs by design"
Incomplete outcome data (attrition bias) All outcomes	High risk	Missing data reported in the original article not accounted for.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	None
Baseline outcome measurements similar?	Unclear risk	Not stated
Baseline characteristics similar?	Low risk	The imbalance between the intervention and control was adjusted and controlled by conducting multivariate logistic regressions.
Adequate protection against contamination?	Low risk	Buffer zones were left between intervention and control clusters to avoid contamination.

Maluccio 2004.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: conducted in Nicaragua (Red de proteccion social) Participants: all households except 169 (2.9% of households that lived in the intervention area) that owned either a vehicle (truck, pickup truck, or jeep) or land > 14.1 hectares, or both
Interventions	Intervention: in 21 clusters Programme had 2 components: Monthly "food security" cash transfer ("bono alimentario" = USD 224 per year = 13% of total amount of household expenditures in beneficiary households before the programme) conditional on attendance at monthly health educational workshops, on bringing their children under age 5 years for free scheduled preventive childcare appointments (which included the provision of anti‐parasitic medication, and vitamins and iron supplements), on having up‐to‐date vaccination, and on adequate weight gain A "school attendance" cash transfer every 2 months (USD 112 per year = 8% of total amount of household expenditures in beneficiary households), contingent on enrolment and regular school attendance of children aged 7 to 13 years. In addition, household received an annual cash transfer per eligible child for school supplies. Beneficiaries did not receive the food or education cash transfers if they failed to comply with any of the conditions. Control: no intervention in the 21 control clusters
Outcomes	Immunisation coverage: reported up‐to‐date vaccination schedule (children aged 12 to 23 months) Health services uptake: attendance at preventive care visits by children Anthropometric or nutritional outcomes: prevalence of stunting, wasting, and underweight (children aged < 5 years) Height for age Z‐score (children aged < 5 years) Prevalence of anaemia
Duration of intervention	2 years
Notes	Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Random selection by balloting within each stratum, randomisation was achieved by blindly drawing one of six coloured balls (three blue for intervention, three white for control) from a box after the name of each comarca [region] was called out"
Allocation concealment (selection bias)	High risk	Randomisation not concealed
Blinding (performance bias and detection bias) All outcomes	High risk	Study not blinded
Incomplete outcome data (attrition bias) All outcomes	High risk	Reasons for attrition not given
Selective reporting (reporting bias)	Low risk	All outcomes stated were reported on.
Other bias	High risk	"In October 2001, then, beneficiaries had been receiving transfers, and the educational components of the program had been monitored for 13 months, but they had only received five months of the health and nutrition services, including the health education workshops" "It is important to emphasize that for most of the indicators considered, the control group also showed large improvements over the period, although on a much smaller scale. A possible explanation for this increase is that other providers are bringing health services into the areas not covered by the program (program providers do not offer or deliver any services to non‐beneficiaries)"
Baseline outcome measurements similar?	Unclear risk	Baseline number of children aged 12 to 23 months with updated immunisation similar between baseline and control
Baseline characteristics similar?	Unclear risk	Baseline characteristics of the intervention and control groups are not stated. Author reported "few significant difference between households (or individuals) in intervention and control groups at baseline", but it was unclear if the differences were related to the outcomes of the review.
Adequate protection against contamination?	High risk	"Control and intervention comarcas [regions] are at times adjacent to one another. A household may be a beneficiary while its neighbour is a nonbeneficiary, particularly in a few cases where boundaries such as roads divide two comarcas. Seeing the activity and the emphasis placed on the RPS objectives may lead non‐beneficiaries to undertake behavior they would not have otherwise. Reasons for such actions could be many ‐ including the possibility that the individuals thought this was a way to become eligible"

Morris 2004.

Study characteristics
Methods	Cluster‐RCT in Honduras
Participants	Participants: households in 70 clusters including pregnant women, new mothers, and children aged < 3 years. Outcome on immunisation was measured in 4359 children at pre‐intervention and 3876 at post‐intervention. Aim: to drive demand, poor households benefited from cash transfer on the condition that they keep up‐to‐date with preventive healthcare services.
Interventions	Intervention A: household monetary incentive in 20 clusters: consisted of distribution of vouchers worth GBP 2.53 to mothers who were registered in the 2000 census who were either pregnant or had a child < 3 years of age to a maximum of 2 children. In addition, mothers with children aged 6 to 12 years enrolled in primary schools in grades 1 to 4 given vouchers worth GBP 3.69 per month. Beneficiaries lost aid if they were not up‐to‐date with routine antenatal care, and well‐child preventive health care and if child did not attend school regularly. Intervention B: service‐level monetary incentive in 10 clusters: quality assurance teams set up at each health centre and trained on basic quality assurance methods. They developed work plans that included minor structural repairs; purchase of equipment, materials, and essential drugs; and money to pay lay assistants. Package included promotion of community‐based nutrition programme for children aged < 2 years. Intervention C: combination of household and service‐level monetary incentives (i.e. Interventions A + B) in 20 clusters Control: standard (routine) care in 20 clusters
Outcomes	Proportion of pregnant women immunised against tetanus Proportion of children aged 93 days to 3 years who received first dose of DTP or pentavalent vaccine (diphtheria, tetanus, pertussis, Haemophilus influenzae type B, hepatitis B) at 42 to 92 days of age Proportion of children aged 1 year immunised against measles
Duration of intervention	1 year
Notes	2 years of follow‐up Funding: this evaluation was funded by the Honduran government, within the framework of a loan from the Inter‐American Development Bank .
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Before randomisation, the municipalities were stratified into five sets of 14 on the basis of the prevalence of childhood malnutrition (stunting).9 Within each stratum, random allocation was achieved by a child drawing coloured balls from a box, without replacement. Thus, the randomisation was both stratified and blocked. The aperture of the box was sufficiently small that once the child had inserted his or her arm, it was impossible for him or her to see the coloured ball"
Allocation concealment (selection bias)	High risk	"From the day of the randomisation onwards, there was no attempt to conceal the allocation..."
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Unclear
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up did not differ significantly across groups with similar reasons, mostly due to change of address.
Selective reporting (reporting bias)	Low risk	All prespecified outcomes were reported.
Other bias	High risk	Service package could not be provided according to the protocol and training on quality assurance was limited to only the introduction. Disbursement of funds for this was only 17% of the budget.
Baseline outcome measurements similar?	High risk	The coverage of DTP1 vaccine in the group receiving intervention C (intervention A + B) was lower than the other 3 groups.
Baseline characteristics similar?	Low risk	Demographic and socioeconomic data for the 4 groups are similar.
Adequate protection against contamination?	High risk	"... it was possible for a household to become eligible for the vouchers by moving into a beneficiary municipality. 14% of children aged < 3 years attended clinics in municipalities other than their municipality of residence 1 month prior to post‐intervention survey"

Murthy 2019.

Study characteristics
Methods	Quasi‐RCT
Participants	Setting: Mumbai (urban slum), India Participants: pregnant mothers
Interventions	Intervention: "The mMitra package consisted of 145 voice messages designed to be shared from when a woman was 6 weeks pregnant until the infant reached 1 year of age. Messages were delivered two times per week during pregnancy; they were clustered at one message per day immediately postpartum for 7 days, and then reduced in frequency back to two messages per week from the second week of infancy. mMitra also provided a free call‐back service within 2 days after the original call was received, in case women wanted to hear the messages they missed or listen to messages again. There were no text messages delivered through this program unlike in other programs." Control: did not receive mMitra messages
Outcomes	The primary outcomes of interest were number of full‐term infants born at or above the ideal birth weight of 2.5 kg and nutritional status at 1 year of age. Secondary outcome was full immunisation of the child.
Duration of intervention	2 years
Notes	Funding: this study was funded by Johnson & Johnson. The funders contributed to critical review of the manuscript and decision to submit the paper for publication.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	“They were systematically assigned to either the intervention or control group. … For every four women enrolled consecutively, the first three were assigned to the intervention group and the last woman was assigned to the control group.”
Allocation concealment (selection bias)	High risk	No concealment of allocation.
Blinding (performance bias and detection bias) All outcomes	High risk	Not blinded. "Data were collected by six female investigators who were part of the research team and went from house‐to‐house."
Incomplete outcome data (attrition bias) All outcomes	High risk	There was greater loss to follow‐up in the intervention group compared to the control group; as‐treated analysis was used.
Selective reporting (reporting bias)	Low risk	All relevant outcomes reported
Other bias	High risk	“The MCH cards were the data source for the primary outcomes; however, only 65% of the available cards in both groups had the necessary anthropometric data. It is unclear how the lack of that data affected the statistical outcome.”
Baseline outcome measurements similar?	Unclear risk	Not indicated
Baseline characteristics similar?	Unclear risk	Insufficient information to support judgement. “There were no statistically significant changes in the demographic characteristics of women in the control group at baseline versus when child is one year of age.”
Adequate protection against contamination?	High risk	“At Time 2, we discovered women in the intervention group who did not receive the messages and women in the control group who indicated that they did receive the messages.”

Nagar 2018.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: rural regions of Udaipur, Rajasthan, India Participants: all mothers with an infant less than 6 months old
Interventions	Intervention: (1) Pendant only ‐ "the immunization record was digitally stored on a pendant with black thread, worn by the child. Unlike the sticker, the pendant is visible, wearable, and culturally significant. (2) Pendant + voice call reminders: children received the pendant as described above and mothers received (automated) voice call reminders the day before and the day of the camp, along with a missed camp message for mothers who failed to attend." Control: Sticker ‐ "Near Field Communication (NFC) stickers were placed on the existing immunization card. These stickers serve as a digital record of the child’s immunization while retaining the paper card that the mother currently uses. The sticker can be updated via our app and allows for consistent methodology of immunization data collection."
Outcomes	DTP3 uptake and timeliness of DTP3 vaccination
Duration of intervention	2 months
Notes	Funding: this study was funded by the Thorne Prize for Social Innovation in Health, the Future Health Systems group at the Johns Hopkins Bloomberg School of Public Health, and the Human Nature Lab at Yale University.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A computerized random allocation sequence was conducted with assistance from the Johns Hopkins Bloomberg School of Public Health prior to enrollment, with balance analysis across all treatment arms."
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	High risk	Neither surveyors nor nurses were blinded to the treatment arms.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analysis based on intention‐to‐treat
Selective reporting (reporting bias)	Low risk	All relevant outcomes were reported.
Other bias	High risk	“There were supply side failures in both immunization camps held and voice calls delivered... Data collection gaps were noted: 9 children in the cohort were missing from the backend and two in the backend were not in the research cohort. … Potential selection bias for the P+V arm was also an issue due to uneven distribution of mobile phone access among all 3 arms, but this imbalance was controlled for in the regression analysis.”
Baseline outcome measurements similar?	Unclear risk	Baseline outcome measures not reported.
Baseline characteristics similar?	Low risk	Baseline characteristics of the study and control groups are reported and similar.
Adequate protection against contamination?	Low risk	No: "During pre‐trial testing, 24 camps had been offered a pendant. To minimize contamination, a computerized randomization was performed to evenly distribute these contaminated pendants among the arms."

Oladepo 2021.

Study characteristics
Methods	Quasi‐experimental cluster
Participants	Mothers of infants aged 0 to 2 months attending immunisation in selected PHCs
Interventions	Intervention: group received immunisation‐related reminder text messages Control: "mothers of infants in the control group did not receive any reminder text messages; however, they were provided with health information flyers on the importance of observing adequate child nutrition and growth monitoring"
Outcomes	Completion of all vaccinations
Duration of intervention	10 months
Notes	0 to 2 months Funding: this project was supported by the Bill and Melinda Gates Foundation, Seattle, WA, under the Grand Challenge Explorations [OPP1182578]. The funder had no role in the study design, data collection and analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quasi‐experimental
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not stated
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	Imbalance in rural, urban selection of clusters in favour of rural.
Baseline outcome measurements similar?	Low risk	All outcomes were reported.
Baseline characteristics similar?	Unclear risk	Not stated
Adequate protection against contamination?	High risk	No protection against contamination

Owais 2011.

Study characteristics
Methods	RCT in Pakistan
Participants	Setting: urban and semi‐urban communities with low literacy and low immunisation coverage Participants: 364 mother‐infant pairs, with infants aged ≤ 6 weeks. Excluded twin births, infants > 6 weeks of age, or infants born to mothers living outside the study surveillance areas. Cut‐off of 6 weeks was used to ensure that the intervention was implemented before the first dose of DTP/hepatitis B became due.
Interventions	Intervention: 3 targeted pictorial messages regarding vaccines administered by trained CHWs. First key message highlighted how vaccines save children's lives. Second message provided logistic information about the address and location of the local vaccination centres. Third key message emphasised the significance of retaining immunisation cards, and the role they could play at the time of the child's school admissions. A copy of these pictorial messages was left with the mother. Messages took about 5 minutes to impart. Control: verbal general health promotion messages delivered by trained CHWs. Messages included information on hand washing, breastfeeding, clean water, benefits of using oral rehydration solutions during diarrhoea, bringing the infant to nearby health centre when there were symptoms of acute respiratory illnesses, importance of antenatal check‐ups for mothers, and some general information on vaccines. Length of each educational session was approximately 10 to 15 minutes.
Outcomes	DTP/hepatitis B vaccine completion (3 doses) at 4 months after enrolment (4 to 5 months of infant's age)
Duration of intervention	4 months
Notes	Community‐based study conducted at 5 low‐income sites in Karachi, Pakistan. Participants were enrolled from August 2008 to November 2008 and followed up for assessment of outcome from December 2008 to March 2009, with each individual mother‐infant pair approached 4 months after the educational intervention session. Funding: two of the study authors were supported by a grant from the Fogarty International Center, National Institute of Health, USA (Grant number: ID43 TW0075 85‐01).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomization lists, stratified for each of the five enrolment sites were generated by a computer and provided to the CHWs. Upon consent, mother‐infant pairs were assigned either to intervention or control arms through block randomisation (n = 4), according to the computer‐generated list"
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	"As the intervention was educational, blinding of study staff and participants was not possible... Outcome assessment was done by an investigator ... blinded to the exposure status of participants"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome data not available for 2% (4/183) in the intervention group (4 deaths) and 3% (5/183) in the control group (3 deaths). The loss to follow‐up was low.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	None
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Low risk	Yes

Oyo‐Ita 2021.

Study characteristics
Methods	Cluster‐RCT
Participants	Traditional and religious leaders, health workers, ward development committees
Interventions	The components of the intervention were: TRL training, health workers’ training, community engagement and strengthening of the ward development committee
Outcomes	Vaccination coverage in children, the dropout rate for Pentavalent 3 vaccine, the timing of Pentavalent and measles vaccination
Duration of intervention	18 months
Notes	Included children 0 to 23 months Funding: the study was funded by a grant from the International Initiative for Impact Evaluation (3Ie). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Each stratum allocated to intervention and control arms by simple random sampling using R by the collaborating institution"
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was not described.
Blinding (performance bias and detection bias) All outcomes	Low risk	The respondents in the survey and the data collectors were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Independent sampling in pre‐ and post‐intervention household surveys.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Low risk	Vaccination coverage was similar between the 2 arms.
Baseline characteristics similar?	Unclear risk	Not sufficiently clearly presented to make a judgement.
Adequate protection against contamination?	Low risk	The selected wards were non‐adjacent to reduce possible contamination.

Pandey 2007.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: India Participants: households with at least 1 child going to public primary school in the village. Immunisation coverage targeted children aged 0 to 35 months.
Interventions	Intervention:information campaign in 11 clusters; 2 rounds of information campaigns consisting of 2 or 3 meetings and distribution of posters and leaflets. 15‐minute audiotaped message played twice at each meeting and 15 minutes given for questions. To ensure uniformity, only questions for which answers were written in the leaflet were responded to. Control: no intervention in 10 control clusters
Outcomes	Received tetanus vaccination Received at least 1 vaccine
Duration of intervention	Each of the 2 rounds of meetings lasted for 1 hour and each round was separated by 2 weeks
Notes	Post‐intervention data collected 12 months after Funding: Sahbhagi Shikshan Kendra (a nongovernmental organisation based in Uttar Pradesh) and the World Bank. The funding organisations aided in the design of the study. They had no role in the collection, management, analysis, or interpretation of the data or in the preparation of the manuscript. World Bank approved the manuscript.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomly generated numbers
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was not described.
Blinding (performance bias and detection bias) All outcomes	Low risk	Research assistants post‐intervention had no knowledge of the intervention.
Incomplete outcome data (attrition bias) All outcomes	Low risk	2.4% loss to follow‐up. Reasons not related to the study.
Selective reporting (reporting bias)	Low risk	No selective reporting suspected
Other bias	Low risk	Not likely
Baseline outcome measurements similar?	Low risk	The difference in the proportion of children immunised at baseline in the 2 groups was not statistically significant.
Baseline characteristics similar?	Low risk	Baseline characteristics were similar.
Adequate protection against contamination?	Low risk	"By randomly selecting only 5 village clusters of about 1000 in each district, we spread the selection of 105 village clusters over 21 districts to minimize any potential for contamination"

Powell‐Jackson 2018.

Study characteristics
Methods	RCT
Participants	Setting: Utta Pradesh, India Participants were 722 mothers of children aged 0 ± 36 months who had not received 3 doses of diphtheria pertussis tetanus (DPT) vaccine.
Interventions	Intervention: information to mothers on the benefits of tetanus vaccine. "There were 2 versions of the script that differed in the way the information was framed. The first framed the information on tetanus vaccination as gains e.g., the child is less likely to get tetanus and more likely to be healthy if vaccinated. The second framed information on tetanus vaccination as a loss e.g., the child is more likely to get tetanus and suffer ill health if not vaccinated. Visual aids were used to help convey the information in an accessible manner to illiterate women, and a Hindi leaflet containing the information was left with the mother. A short question and answer session followed the provision of the information to ensure comprehension of the information. The intervention took about 10 minutes to deliver. Both variants of the intervention informed mothers where in the public sector they could get their child vaccinated." Control: no information was given to the mother
Outcomes	The primary outcome was the proportion of children who had received DPT3 measured after 7 months of follow‐up. Secondary outcomes were the proportion of children fully vaccinated against tuberculosis, diphtheria, pertussis, tetanus, and measles; the mother's knowledge of any symptom of tetanus; and the mother's perception of the efficacy of tetanus vaccination.
Duration of intervention	7 months
Notes	Funding: the research was supported by funding from Merck, through its Merck for Mothers program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A computer random number generator in CSPro (version 6.1) assigned participants to 1 of the 3 study arms during the baseline visit."
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Low risk	“Field staff were blinded to group assignment in the endline survey. ... The primary analysis was done blinded to treatment group assignment.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	"A total of 16 (2.2%) participants were lost to follow‐up, resulting in a final analytical sample of 706. There were no further missing data. Attrition was similar across treatment groups. The analysis was by intention to treat."
Selective reporting (reporting bias)	Low risk	All relevant outcomes were reported.
Other bias	High risk	"We did not achieve the target sample size for the treatment group analysis such that the study was underpowered to detect small differences between the 2 intervention groups.. We were unable to locate more than 400 potentially eligible women who could not be found at home. This may have limited the extent to which our study sample was representative of the wider population."
Baseline outcome measurements similar?	Low risk	"Participants in the 3 groups were similar in terms of child age, child vaccination coverage, knowledge, perceptions of efficacy, and access to health facilities."
Baseline characteristics similar?	Low risk	"These data also suggest the treatment arms were well balanced."
Adequate protection against contamination?	Low risk	“We conducted an individual rather than a cluster randomised controlled trial, making contamination a potential concern. However, the information was given in private, and our analysis suggests that the outcomes of neighbours were not influenced by their proximity to treated households. If contamination was present, our results would provide an underestimate of the effect of the information intervention."

Robertson 2013.

Study characteristics
Methods	Matched, cluster‐RCT
Participants	Setting: Manicaland, Zimbabwe Participants: "Eligible households contained children younger than 18 years and satisfied at least one other criteria: head of household was younger than 18 years; household cared for at least one orphan younger than 18 years, a disabled person, or an individual who was chronically ill; or household was in poorest wealth quintile."
Interventions	Intervention: unconditional cash transfers in 1525 households, conditional cash transfers in 1319 households Control: no intervention in 1199 households
Outcomes	3 domains of child well‐being (identity, health, and education) Proportion of children aged < 5 years with a birth certificate Proportion of children aged < 5 years with up‐to‐date vaccinations (measles, BCG, polio, and DTP) Proportion of children aged 6 to 12 years attending school at least 80% of the time in the previous month
Duration of intervention	13 months
Notes	Funding: this trial was funded by the Wellcome Trust, the World Bank through the Partnership for Child Development, and the Programme of Support for the Zimbabwe National Action Plan for Orphans and Vulnerable Children (administered by UNICEF Zimbabwe). The Wellcome Trust and World Bank had no role in study design, data collection, data analysis, data interpretation, or writing of the report. UNICEF Zimbabwe was involved in study design. The lead author had full access to all the data in the study and had final responsibility for the decision to submit for publication.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Allocation was done by drawing of lots from a hat.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was not described.
Blinding (performance bias and detection bias) All outcomes	High risk	"Participating households and individuals delivering the intervention were not masked to cluster assignment. ... research assistants were not told the allocation of the household they were interviewing, however, questions were included at the end of the qustionnaire about whether household received transfers. LR was masked while doing the primary analysis"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Independent sampling at baseline and endline surveys.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	2 villages randomised into the control group were mistakenly enrolled in the unconditional cash transfer group. The duration of the study was shortened from 24 to 13 months due to lack of funds.
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	Most of the characteristics were similar across groups.
Adequate protection against contamination?	High risk	Though the authors "used cluster randomisation to reduce conflict and contamination between households, which could arise if neighbouring households received different interventions", it was reported that "in the UCT group, 400 (31%) of 1297 eligible households that reported receiving cash also reported having to meet conditions (data for conditions missing for five households), suggesting some contamination between the UCT and CCT groups."

Sengupta 2017.

Study characteristics
Methods	Non‐randomised controlled trial
Participants	Setting: residents in Municipal Corporation of Ludhiana slum area Participants: "‘Newer migrants’ (those who migrated to the city 30 days to 10 years ago) were selected for this study …"
Interventions	Intervention: "…the research team from Christian Medical College Ludhiana (CMCL) worked with the Civil Surgeon and government Medical Officers responsible for the area as well as the community (via community leaders and the formation of active community groups) to establish a government funded outreach vaccination programme in settings provided by the community. In addition, the community itself took responsibility for nominating adult guardians (community guardians) who would be present in the parent’s absence to provide consent and post‐immunization surveillance to ensure the child’s well‐being." Control: no community outreach
Outcomes	BCG, OPV, DPT, Hep vaccine, measles uptake
Duration of intervention	12 months
Notes	Funding: the Indian Council of Medical Research (ICMR), New Delhi research grant under IRIS ID 2010‐1259E.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Not an RCT
Allocation concealment (selection bias)	Unclear risk	Not described, probably not done
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition was about 2% in the 2 arms of study.
Selective reporting (reporting bias)	Low risk	All relevant outcomes reported
Other bias	Unclear risk	Unclear
Baseline outcome measurements similar?	Unclear risk	Though vaccination uptake was reported to be slightly better for some vaccines in the intervention clusters at baseline, it is unclear if the difference was statistically significant. However, the difference in the completion of the immunisation schedule in the intervention and control clusters was not statistically significant.
Baseline characteristics similar?	High risk	"More respondents from control communities were aware of the benefits of vaccines for disease prevention..."
Adequate protection against contamination?	Unclear risk	Not stated

Siddiqi 2020.

Study characteristics
Methods	RCT
Participants	Caregivers
Interventions	Intervention: "two intervention groups comprised of two different types of immunization reminder bracelets. … Group A was provided with a bracelet developed by Alma Sana Inc, adapted for Pakistan’s EPI schedule. The final adapted bracelet had the recommended age of the child denoted in weeks/months for receiving the vaccine followed by symbols representing each of the vaccines due at that age. Intervention Group B was provided with a simple silicone bracelet “Star Bracelet” that consisted of six symbols (five crescents and one star) denoting the six visits that the child is supposed to make to the immunization clinic to complete the routine immunization schedule." Control: the vaccinator recorded the child’s immunisation data in the EPI immunization card provided to the caregivers.
Outcomes	Penta 3 and measles 1 coverage
Duration of intervention	12 months
Notes	Funding: this study was funded by the Harvard Medical School Center for Global Health Delivery‐Dubai. The funding organization had no role in the design of this study and did not have any role during its execution, analyses, interpretation of the data, or decision to submit results.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The randomization sequence was generated in Stata version 13 using random block sizes of 3, 6, 9 and 12."
Allocation concealment (selection bias)	Low risk	"The allocation sequence was concealed from the study staff responsible for screening and enrolling participants in sequentially numbered, opaque, sealed envelopes and was only revealed post‐randomization."
Blinding (performance bias and detection bias) All outcomes	High risk	Blinding was not done, which could have influence performance and detection bias.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"We analyzed data using the intention‐to‐treat population between groups."
Selective reporting (reporting bias)	High risk	Coverage of OPV3, PCV3 not reported
Other bias	Low risk	Not suspected
Baseline outcome measurements similar?	Low risk	Yes. Similar in the intervention and control arms
Baseline characteristics similar?	Low risk	"The baseline characteristics of study participants in both groups at the time of enrolment were similar for the majority of the variables."
Adequate protection against contamination?	Unclear risk	Information not provided

Todd 2010.

Study characteristics
Methods	RCT
Participants	Women admitted to obstetric care who were in a stable condition and not imminently delivering (complete dilatation)
Interventions	The intervention utilised “a new cadre of healthcare worker to provide intrapartum hepatitis B surface antigen (HBsAg) rapid testing (control) and post‐partum concentrated counseling (intervention) to obstetric patients admitted to any of the four Kabul maternity hospitals as compared to usual care.”
Outcomes	"The key outcomes of interest are correct breastfeeding practices, completion of infant vaccination, and use of contraception postpartum."
Duration of intervention	12 months
Notes	Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Experimental arm assignment was designated by recruitment date due to staffing availability, with dates randomly selected at each hospital assuming enrollment of 12 participants/session using a computer‐generated list.”
Allocation concealment (selection bias)	Low risk	Ballot drawn from brown envelope
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No information to make judgement
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Unclear risk	"Next, while vaccination dates were recorded directly from the infant record, there were numerous entries, particularly the last injection in a series, that was ticked but without a date recorded. Staff inquiries generally established that the missing date was due to OPV administered by a NID representative in the home. However, NID dates were used for missing DPT vaccination data, which does not reflect the vaccine administered. The entry was counted as the family attested to the receipt of the vaccine but this retention may have lead to a higher reported DPT completion rate and blunted any intervention effect."
Baseline outcome measurements similar?	Low risk	Yes
Baseline characteristics similar?	Low risk	"There were no significant differences between demographic variables, prior contraceptive use, breastfeeding, or child vaccination."
Adequate protection against contamination?	Unclear risk	Not stated

Uddin 2016.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: Sunamgongj district and Dhaka city, Bangladesh, India Participants: pregnant women, mothers with children age 0 to 11 months, and EPI service providers in study areas
Interventions	Intervention: “mTika sent one SMS one day before a scheduled EPI session, a second SMS at opening time on the day of the EPI session, and a third SMS two hours before closing time on the day of the EPI session. Symbols taught to mothers at registration were used in SMS messages for mothers who were illiterate. EPI providers could access mTika from smart phones to check the number and vaccination details of target children due for a given EPI session. Health workers would log administered vaccines into mTika, and mTika then would update automatically future vaccination timetables and reminders. At the end of an EPI session, mTika would highlight children who did not show. EPI supervisors could access mTika from the web to monitor vaccinators’ daily performance.” Control: not stated
Outcomes	Full vaccination
Duration of intervention	1 year
Notes	Funding: this research was funded by Grand Challenges Canada (GCC).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Authors reported the study as being quasi‐experimental. However, the description of the randomisation was adjudged to be low risk as shown in this quote: "we used two‐stage random cluster sampling first to select community clusters within study areas and then to select households within clusters. We used the World Health Organization (WHO) cluster‐sampling methodology to randomly select 40 clusters within each of our two control and two intervention study areas:..."
Allocation concealment (selection bias)	Unclear risk	No information
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	"... cross‐sectional baseline and endline surveys of vaccination coverage among children 0–11 months old in control and intervention areas."
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Unclear risk	Not stated
Baseline outcome measurements similar?	Unclear risk	Not stated
Baseline characteristics similar?	Unclear risk	Not stated
Adequate protection against contamination?	Unclear risk	Not stated

Usman 2009.

Study characteristics
Methods	RCT in Pakistan
Participants	Setting: urban setting in Pakistan Participants: 375 mothers visiting the EPI centre in each of 4 arms of study with 1125 children registering for DTP1 immunisation and residing in the study area for the past 6 months
Interventions	Intervention A: redesigned ("reminder‐type") immunisation card; a larger card (15.5 cm by 11.5 cm when folded) that had only the date and day of next immunisation on both sides of the outer card printed with Microsoft Word font size 42 was designed as a reminder for mothers/carers for immunisation. Inner side of the card contained information about the child's complete immunisation schedule dates and instructions for the mother/carer. For those in the arm with the redesigned card, the date and day for each DTP vaccination was written on the outer side of the card; dates of previous vaccinations were crossed out to avoid confusion. Mother was advised to place the card at a frequently visible place at home and to bring it to the clinic during immunisation visits. Intervention B: centre‐based education; clinic‐based education that lasted 2 to 3 minutes given to mothers at enrolment of their children in the EPI centre. The health education emphasised the importance of immunisation schedule completion. Intervention C: intervention 1 + 2 Control: standard care
Outcomes	Number of enrolled children with DTP3 completed within 90 days of duration of study
Duration of intervention	2 to 3 minutes per session; follow‐up for 90 days
Notes	Urban Pakistan Funding: this study was funded by the University Research Council (URC) of the Aga Khan University, Karachi. The funding agency had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Allocation sequence was by computer‐generated randomisation list.
Allocation concealment (selection bias)	High risk	"The Principal Investigator provided a computer‐generated randomisation list to each enrollment center. The randomization list indicated the study group against each study ID. Each enrolled mother–child unit received a study ID and was assigned to a study group as indicated on the randomization list"
Blinding (performance bias and detection bias) All outcomes	High risk	Neither the participant nor the assessor was blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up
Selective reporting (reporting bias)	Low risk	All outcomes were reported
Other bias	Low risk	No other bias detected
Baseline outcome measurements similar?	Low risk	Not applicable
Baseline characteristics similar?	High risk	Most of the socioeconomic variables were similar, but ownership of a television was higher among the group receiving education and a higher proportion of those receiving standard care lived close to the facility than those in the redesigned card group.
Adequate protection against contamination?	Unclear risk	Unclear

Usman 2011.

Study characteristics
Methods	RCT in Pakistan
Participants	Setting: rural setting in Pakistan Participants: 1508 mother‐child pairs visiting selected EPI centres for DTP1 who were resident in study area for at least 6 months. Criterion used to exclude 2 groups of temporary residents: women who temporarily relocated to their mothers' houses to deliver their children and internally displaced families who had migrated to the study area to avoid the aftermath of 2005 earthquake in the north of Pakistan.
Interventions	Intervention A: redesigned ("reminder‐type") immunisation card; a larger card than the existing EPI card (15.5 cm by 11.5 cm when folded), placed in a plastic jacket and provided with a hanging string. A "trained interviewer pasted the upcoming date and day of DTP2 immunization on both outer sides of the card and showed it to the mother. Mother was asked to hang the card in her home at a frequently visible place and requested that she bring the card along on her next immunization visit to the EPI centre. At DTP2 visit, the interviewer crossed out the date and day for DTP2 visit to avoid any confusion to the mothers, pasted the date and day for the upcoming DTP3 immunization visit on both sides of the card and showed the information to the mother." The inner side of the card contained information about the child's complete immunisation schedule dates and instructions for the mother. Intervention B: centre‐base education; 2‐ to 3‐minute conversation between trained study interviewer and mother to convey the importance of completing the immunisation schedule and the potential adverse impact of incomplete immunisation on the child's health. Session was in simple vocabulary in the local language and deliberately kept short in prevision of potential large‐scale use by EPI staff in the future. Intervention C: combination of redesigned card and centre‐based education Control: standard care, i.e. routine EPI centre visit and neither intervention
Outcomes	DTP3 coverage at the end of day 90 post‐enrolment.
Duration of intervention	2‐3 minutes per session; follow‐up at 90 days
Notes	Rural areas around Karachi, Pakistan. Despite a small purchase volume, the cost of each card including the plastic jacket was USD0.05 Funding: This study was funded by the Sparkman Center for Global Health and NIH grant D43TW005497, the University of Alabama at Birmingham‐Aga Khan University International Maternal and Child Health Research and Training (IMCHRT) program. The funders had no role in the study design, data collection and analysis, the decision to publish, or preparation of the manuscript
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The lead investigator provided a computer‐generated randomisation list to each enrolment centre"
Allocation concealment (selection bias)	High risk	"The Principal Investigator provided a computer‐generated randomisation list to each enrollment center. The randomization list indicated the study group against each study ID. Each enrolled mother–child unit received a study ID and was assigned to a study group as indicated on the randomization list"
Blinding (performance bias and detection bias) All outcomes	High risk	"Because of the overt nature of interventions, neither the study participants nor the interviewers enrolling the study participants and recording the study outcome were blinded to the type of intervention received by the study participants"
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	Low risk	No other bias detected
Baseline outcome measurements similar?	Low risk	Not applicable
Baseline characteristics similar?	Low risk	Yes
Adequate protection against contamination?	Low risk	"Interventions were provided in a private space to prevent contamination between study groups"

Wallace 2019.

Study characteristics
Methods	Cluster‐RCT
Participants	Setting: 5 districts in Indonesia’s West Java province (Cianjur, Cirebon, Kota Bundung, Kota Depok, and Sukabumi) Participants: caregivers of children attending health facility for child's vaccination and care providers in the health facilities
Interventions	Intervention: "In HBR‐only study group health facilities, healthcare providers were instructed to provide an HBR to a caregiver of a child any time the caregiver had not yet received an HBR or had forgotten to bring the HBR to the vaccination visit. If the HBR was a replacement, the provider was to update the replacement HBR with information from the vaccination register. The provider was instructed to tell the parent to keep the HBR at home and to remember to bring it back at the next vaccination visit. In the HBR + sticker intervention health facilities, healthcare providers followed the same HBR provision rules as those in the HBR‐only study group, but also affixed a future vaccination visit reminder sticker to the front of the home‐based record for children still due for a future vaccination, wrote the date of the next vaccination visit on the reminder sticker, and explained the purpose of the sticker to the caregiver. The sticker was bright yellow, approximately 50 mm in width and 12 mm in height, and had a back adhesive that was removed when the provider applied the sticker to the HBR. All children coming for vaccination were eligible for this intervention." Control: "In control study group health facilities, healthcare providers followed their usual practice for vaccination reminders, home‐based record provision, and home‐based record storage location."
Outcomes	The primary outcome of interest was for children to receive DTPcv3 before the end of the study Secondary outcomes were timeliness of a DTPcv3, and time to DTPcv3
Duration of intervention	7 months
Notes	Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The facility sampling frame was first stratified by district; then, within each district, six facilities were randomized to each study group using simple random sampling, for a total of 30 randomized facilities per group."
Allocation concealment (selection bias)	Low risk	Randomisation was at the health facility level into study groups and allocation was done at the start of the study.
Blinding (performance bias and detection bias) All outcomes	High risk	The study was not blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"Primary analyses were intent to treat (ITT), with individuals analyzed according to the group with which their facility was randomized."
Selective reporting (reporting bias)	Low risk	All outcomes were reported.
Other bias	High risk	"It is possible that the sweeping activities succeeded in catching up those children who were missed, while in the HBR + sticker intervention group, those children who would have been vaccinated through sweeping instead ended up coming to the facility due to the effect of the sticker as a reminder of the next vaccination visit."
Baseline outcome measurements similar?	Low risk	"Most baseline indicators were similar across study groups."
Baseline characteristics similar?	High risk	Children in the HBR‐only study group were generally older at time of Penta1 vaccination (88 days of age versus 77 to 79 days) and less likely to have received Bacillus Calmette–Guérin (BCG) vaccination (90% versus 95%) at baseline compared with children in the other 2 groups.
Adequate protection against contamination?	Low risk	"To reduce possible confounding by district, the facility sampling frame was first stratified by district ..."

BCG: Bacille Calmette‐Guérin; CHW: community health worker; DTP: diphtheria‐tetanus‐pertussis; EPI: Expanded Programme on Immunization; HBV3: three doses of hepatitis B vaccine; HBR: home‐based records; IPC: interpersonal communication; IPV: injectable polio vaccine; MCH: maternal and child health; MMR: measles, mumps, rubella; OPV: oral polio vaccine; P4P: pay for performance; PHC: primary health care; RCT: randomised controlled trial; TRL: traditional and religious leaders; WHO: World Health Organization.

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Afzal 2017	Reminder/recall
Ahanhanzo 2016	Programme evaluation
al Teheawy 1992	Retrospective study
Ali 2015	No review outcome was reported
Alto 1989	Observational study
Aneni 2013	Observational study
Anjum 2004	A controlled before‐and‐after study with a single unit for intervention and control arms
Attanasio 2005	No relevant data on outcome
Balogun 2021	Before‐and‐after study using only one site
Balraj 1986	Programme evaluation
Bandyopadhyay 1996	Observational study
Barham 2009	Programme evaluation
Bazos 2015	No relevant data on outcome
Berhane 1993	No relevant outcome; reports on dropout rate
Berman 1991	Observational study
Berry 1991	Observational study
Bishai 2002	No relevant data on outcome
Bossio 2019	Reminder/recall
Briere 2012	A controlled before‐and‐after study with one single unit of intervention and control arms
Brown 2016	One cluster per study arm
Brown 2017	One cluster per study arm
Buser 2021	No comparison between control and intervention arms
Busso 2015	Review outcome not reported
Chandir 2010	Observational study
Chelagat 2020	No outcome of interest reported
Chen 1976	Retrospective study
Chen 1989	Observational study
Cutts 1990	Observational study
Cutts 1994	Observational study
Dammann 1990	Observational study
Dini 1995	No relevant data on outcome
Dominguez Ugá 1988	Observational study
Dougherty 2020	No data to compare intervention and control arms
Edmond 2020	Cross‐sectional study
Ekunwe 1984	Observational study
Gokcay 1993	Descriptive study
Gomber 1996	Observational study
Haji 2016	Single cluster per arm of study
Hayford 2014	Observational study
Hong 2005	Observational study
Hu 2015	A controlled before‐and‐after study with a single unit for intervention and control arms
Hu 2018	Non‐routine vaccine
Igarashi 2010	A controlled before‐and‐after study with a single unit for intervention and control arms
Johri 2015a	No report on effectiveness of the intervention
Johri 2020	No outcome of interest reported
Kaewkungwal 2015	Observational study
Kazi 2017	Comment on reminder/recall
Kuhn 1990	Observational study
Kumar 1990	Observational study
Kuppuswamy 2016	Conference abstract; full text inaccessible
Lechtig 1981	A controlled before‐and‐after study with a single unit for intervention and control arms
Lin 1971	Observational study
Linkins 1995	Observational study
Maher 1993	Observational study
Main 2001	Observational study
Manyazewal 2018	Has one data point at baseline and two after intervention
Marshall 2007	Retrospective study
Merilind 2015	Retrospective study
Ndiritu 2006	Observational study
Nguyen 2017	Descriptive study
Oladeji 2019	Study had only one site for intervention and control respectively
Osinka 2000	Observational study
Pan 1999	Observational study
Patel 2018	Only one study site per arm of study
Pierce 1996	A controlled before‐and‐after study with a single unit for intervention and control arms
Pramanik 2018	Study protocol
Prinja 2010	A controlled before‐and‐after study with a single unit for intervention and control arms
Przewlocka 2000	Observational study
Rahman 2013	A controlled before‐and‐after study with a single unit for intervention and control arms
Robinson 2001	Observational study
Ryman 2011	Data not summarised by the study groups
San Sebastian 2001	Observational study
Sato 2020	Outcomes reported were number of vaccines administered
Seth 2018	Reminder/recall
Shaikh 2003	Observational study
Shapira 2018	No report on outcome of interest
Sutanto 1999	Observational study
Tyminska 2017	No outcome of interest reported
Uddin 2010	A controlled before‐and‐after study with a single unit for intervention and control arms
Uddin 2012	Study had no control arm
Uskun 2008	Observational study
Vaidyanathan 2019	No comparison between control and intervention arms of study
van Zwanenberg 1988	Observational study
Wakadha 2013	No outcome of interest
Wang 2007	No relevant outcome for the review
Wang 2015	No outcome of interest reported
Zeng 2020	No outcome of interest reported
Zimicki 1994	Observational study

Characteristics of studies awaiting classification [ordered by study ID]

Chandir 2022.

Methods	RCT
Participants	Children visiting a study immunisation clinic for BCG, Penta‐1, or Penta‐2 vaccine
Interventions	Participants were randomly divided into 7 study arms comprising 5 incentive arms with varying size (amount), 1 reminder (SMS) arm, and 1 control arm. The incentive arm varied by amount, schedule, design, and payment method. Children were enrolled at BCG, pentavalent‐1 (penta‐1) or pentavalent‐2 (penta‐2) vaccination and followed until at least 18 months of age.
Outcomes	The primary outcome was the proportion of fully immunised children (FIC) at 12 months of age.
Notes	Location: Pakistan

Ibraheem 2021.

Methods	nRCT
Participants	Mother‐infant pairs presenting for the first vaccination appointment
Interventions	Intervention groups were reminders via calls (A), SMS reminders (B), immunisation fact SMS messages (C) and controls on usual care (D). Reminders were made a day before the appointment while SMS immunisation facts were sent at 5 weeks, 9 weeks and 8 months.
Outcomes	Full vaccination
Notes	Location: Nigeria

Mekonnen 2021.

Methods	RCT
Participants	Mother‐infant pairs
Interventions	Participants assigned to the intervention group received mobile phone text message reminders 1 day before the scheduled vaccination visits.
Outcomes	Full and timely completion of vaccinations
Notes	Location: Ethiopia

Oyo‐Ita 2021b.

Methods	Cluster‐RCT
Participants	Children 0 to 23 months
Interventions	Multi‐faceted interventions that included traditional and religious leaders
Outcomes	Cost‐effectiveness analysis
Notes	Location: Nigeria

BCG: Bacille Calmette‐Guérin; nRCT: non‐randomised controlled trial; RCT: randomised controlled trial.

Differences between protocol and review

We have changed the first primary outcome from 'Number of children aged two years fully immunised per vaccine' in the previous version of this review to the first primary outcome 'Proportion of children who received DTP3 by one year of age' in this present review. The latter is a widely accepted standard measure of a childhood immunisation programme's ability to reach the target population. We have also included M‐health interventions due to their wide use in the study setting.

Contributions of authors

AO: screening, data extraction, analysis, and write up

OO: screening, data extraction, and write up

DA: screening, data extraction, and write up

EE: analysis and write up

EEs: write up

YB: statistical analysis

MC: write‐up

CO: screening and data extraction

CN: data extraction

CW: review and write‐up

MM: review and write‐up

Sources of support

Internal sources

• Cochrane Nigeria, University of Calabar Teaching Hospital, Nigeria

  Support resources for staff working on the review.

External sources

• No sources of support provided

Declarations of interest

Angela Oyo‐Ita: is an author of one of the included studies (Oyo‐Ita 2021). She did not perform data extraction, risk of bias, or GRADE assessment for that study.

Olabisi Oduwole: is an author of one of the included studies (Oyo‐Ita 2021). She did not perform data extraction, risk of bias, or GRADE assessment for that study.

Dachi Arikpo: is an author of one of the included studies (Oyo‐Ita 2021). She did not perform data extraction, risk of bias, or GRADE assessment for that study.

Ekpereonne Esu: is an author of one of the included studies (Oyo‐Ita 2021). He did not perform data extraction, risk of bias, or GRADE assessment for that study.

Moriam Chibuzor: none known.

Emmanuel Effa: is a Cochrane Editor but was not involved in the editorial process for this review.

Yusenthua Balakrishna: none known.

Charles S Wiysonge: none known.

Chioma M Oringanje: none known.

Chukwuemeka E Nwachukwu: none known.

Martin M Meremikwu: is an author of one of the included studies (Oyo‐Ita 2021). He did not perform data extraction, risk of bias, or GRADE assessment for that study.

New search for studies and content updated (no change to conclusions)