Multicomponent interventions to improve routine childhood vaccine uptake in low and middle-income countries: a scoping review protocol

Abstract

Introduction

Vaccine coverage remains inequitable globally. Many systematic reviews have looked at the effectiveness of strategies to improve vaccine uptake; however, these reviews frequently lack data from low and middle-income countries (LMICs), where evidence of cost-effective strategies is most valuable. This is partly because reviews often exclude non-randomised, observational or unpublished evaluations that are common in LMICs. Many reviews also exclude multicomponent interventions due to challenges isolating the effect of each component. A comprehensive mapping of multicomponent interventions implemented in LMICs would increase the visibility of studies excluded from systematic reviews and improve comparability of future evaluations by providing guidance for researchers on evaluation frameworks. This scoping review aims to identify, compare and summarise the properties and evaluation methods of multicomponent interventions to improve uptake of routine childhood vaccines in LMICs, and to assess the strengths and limitations of evaluation frameworks applied.

Methods and analysis

This review will be conducted using the Joanna Briggs Institute methodology for scoping reviews and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses Extension for Scoping Reviews guidelines. We will search the following databases: MEDLINE, Embase, PubMed, Cochrane, Eldis and Global Health (CAB Direct), Global Index Medicus, 3ie Portal, Google Scholar, COnnecting REpositories, and reference lists. One author will screen titles and abstracts and extract data from included articles using a pretested data extraction template. Uncertainties will be resolved through discussion with another author. Only studies published in English will be included for full review. We will assess the practicability, applicability, sensitivity and specificity of the evaluation frameworks used and present results using descriptive statistics, summary tables and charts.

Ethics and dissemination

Ethics approval is not required. The review will be submitted as part of a doctoral thesis, presented at conferences and published in peer-reviewed journals.

Study registration

https://osf.io/7r84g.

Strengths and limitations of this study.

• The search strategy includes multiple databases of peer-reviewed literature as well as a broad range of grey literature sources.

• The review’s approach could improve the visibility of studies typically excluded from systematic reviews that are still an important part of the evidence base.

• There is no meta-analysis or formal assessment of study quality planned for this scoping review.

• Studies in all languages will be included in the initial searches, however, only those published in English will be included for full-data extraction.

Introduction

Immunisations save millions of lives every year, yet vaccine coverage remains inequitable within and between countries.^{1 2} The poorest, most vulnerable and most marginalised populations frequently face the greatest barriers to accessing immunisation services.^{1 3} Despite the availability of safe and effective childhood vaccines, in 2021 an estimated 25 million eligible children did not receive the diphtheria, tetanus and pertussis vaccine—an increase of 6 million from 2019.⁴ Most of these children live in low and middle-income countries (LMICs). Vaccine inequity also exists for adults in LMICs, with COVID-19 vaccination rates lagging behind those of high-income settings.⁵

Understanding which strategies work, how they work and in what context is essential for improving vaccine coverage. Prioritisation of effective strategies is particularly important for ensuring equitable access to high-quality immunisation services in settings with limited resources.^{3 6} Systematic reviews are an important source of evidence to inform policy and programmatic decisions, and many reviews have assessed the effectiveness of strategies aimed at improving vaccine uptake among children, adolescents and adults.^7–16 According to these reviews, there are numerous interventions that can successfully improve vaccine uptake in specific settings and populations including educational interventions, reminders, outreach services, household incentives, home visits, school-based programmes and integration of immunisation services with other services.8 10 13–15 17 18

However, the body of evidence from systematic reviews is incomplete, particularly in relation to LMICs, for two key reasons. First, data from LMICs are scarce because systematic reviews are often limited to randomised controlled trials, excluding observational and unpublished evaluations that are common in LMICs. While the majority of under-vaccinated and unvaccinated children live in LMICs, most of the published literature is from high-income settings, with very different health system capacities, resource availability and health priorities. Programmes aimed at strengthening immunisation services are common in LMICs, however, they are not always documented in the peer-reviewed research literature or are not set up as randomised-controlled trials, and are therefore not included in systematic reviews.¹⁹ A scoping review commissioned by the WHO to examine systematic reviews and meta-analyses on interventions to improve vaccine uptake across all age groups found that only 12% of reviews contained data from LMICs.^{19 20}

Second, interventions with multiple components are often excluded from systematic review meta-analyses due to challenges isolating the effect of each component. This is an issue because individual studies suggest that multicomponent interventions—those with more than one purpose or format of delivery—are particularly effective at improving vaccine coverage.^{14 18 19} Vaccine uptake behaviour has many drivers, including social influences, vaccine confidence, motivation and practical issues,^{20 21} and multicomponent interventions can address several drivers concurrently. However, such interventions are challenging to evaluate due to their complexity. They are often excluded from systematic reviews because the interventions are not clearly described or the effect of each component cannot be isolated.¹⁰

Multicomponent interventions implemented and evaluated in LMIC settings, which may be the most relevant to LMIC vaccine programmes and policies, are falling through the gaps in the ‘gold standard’ systematic review evidence base. The first step in filling this gap is understanding what these interventions look like, where they have been implemented, what components are commonly combined and how they are combined. To improve the future of this evidence base, it is also necessary to understand and appraise the appropriateness of the frameworks and methods that have been used to evaluate their effectiveness.²² There is one existing evidence review on multicomponent interventions to increase the uptake of routine vaccines.²³ However, this review focuses only on countries within the Organisation for Economic Co-operation and Development, includes studies with more than two intervention components and does not assess the suitability of the evaluation methods used in the included studies.

Evaluation frameworks are one way to mitigate the complexities of systematically assessing the effectiveness of a multicomponent health intervention. These frameworks can facilitate the development of clear objectives and methods appropriate to the specific research question and can help to assess the impact of context on implementation.²⁴ Evaluation frameworks also have the potential to improve the quality of evidence generated by evaluations as well as improve comparability between studies.²⁵ There are many evaluation frameworks available in the literature including those developed specifically for public health programmes such as the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework²⁶; frameworks aimed at particular intervention types such as the United Kingdom Medical Research Council’s guidance on evaluating complex health interventions²⁷ and broader frameworks applicable to a range of contexts such as realist evaluation.²⁸ Reviews of evaluation frameworks used for public health and behaviour change interventions have been undertaken,^{24 25} however, none have specifically identified the frequency or appropriateness of the frameworks used to evaluate interventions aimed at improving vaccine uptake.

This scoping review aims to identify, compare and summarise the properties and evaluation methods of multicomponent interventions to improve the uptake of routine childhood vaccines in LMICs, and to assess the strengths and limitations of the evaluation frameworks. A comprehensive mapping of these multicomponent interventions and the methods used to evaluate them will improve the comparability and consistency of future evaluations by providing guidance for researchers on evaluation frameworks and outcome measures. It will also improve the visibility of studies excluded from systematic reviews that may still be useful for decision-makers in LMICs.

Methods and analysis

Scoping reviews can be used to identify and map the existing evidence more broadly, including study designs and grey literature that would be excluded from systematic reviews and identifying study components that are not commonly delineated in systematic reviews such as evaluation frameworks.^29–31 A scoping review will allow us to obtain a comprehensive overview of multicomponent interventions to improve vaccine uptake in LMICs and the methods used to evaluate them.

Protocol design

The proposed scoping review will be conducted using the Joanna Briggs Institute (JBI) guidance on scoping reviews,^31–33 and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses Extension for Scoping Reviews (PRISMA-ScR).³⁴

Developing the research question

We developed our research questions based on key gaps highlighted in previous reviews10 13–15 35 and through consultations within the research team. This scoping review aims to answer the following questions:

1. What multicomponent interventions have been used to improve uptake of routine childhood vaccines in LMICs?

   1. What components are most frequently used and in what context? What components are most frequently used in interventions described as effective?

   2. How are the components combined?

2. How have multicomponent interventions to improve uptake of routine childhood vaccines in LMICs been evaluated?

   1. What outcomes have been measured and using what methods?

   2. What frameworks have been used to guide evaluation methods?

   3. What are the strengths and limitations of the evaluation frameworks used?

Eligibility criteria

Our review will use the JBI approach to inclusion criteria of Population, Concept and Context. These components are outlined below.

Population

For the purposes of this review, population can refer to the group of people targeted by the vaccine programme (infants or children), or the group targeted by the intervention to improve vaccine uptake (eg, healthcare providers). We will therefore include children under 5 years of age or those responsible for making vaccination decisions for them (eg, parents or caregivers) and any population targeted by an intervention to improve vaccine uptake.

Concept

Descriptions of interventions that aim to improve uptake of routine childhood vaccines and have more than one component with a distinct purpose (eg, to inform or educate, to teach skills) or format/method of delivery (eg, printed material, face to face education, policy mechanism). Interventions aimed at improving uptake of any routine childhood vaccine will be included. Studies of interventions with only one component will be excluded.

Context

Studies with data from any LMIC will be included. The definition of LMICs will be based on the World Bank division of countries into four income groupings and will include those in the low, lower-middle and upper-middle groups.³⁶ Studies with data from high-income countries only will be excluded. Where studies report results from a combination of low or middle-income and high-income settings, only data from the LMICs will be extracted if possible.

Types of sources

In this scoping review, we will include: experimental and quasi-experimental study designs such as randomised controlled trials, non-randomised controlled trials, before and after studies and interrupted time-series studies; analytical observational studies including prospective and retrospective cohort studies, case-control studies and analytical cross-sectional studies; descriptive observational studies; and evaluations including process, outcome and impact evaluations. Studies with no control and those that only use qualitative methods will not be included. We will include peer-reviewed publications and grey literature reports, such as evaluation reports, policy documents and research theses.

Search strategy

The search strategy will aim to locate both published and unpublished studies. An initial limited search of MEDLINE was undertaken to identify articles on the topic. The text words contained in the titles and abstracts of relevant articles, the index terms used to describe the articles and the search strategies of other published scoping and systematic reviews13 14 19 23 37 were used to develop a full-search strategy for MEDLINE (see online supplemental appendix 1). The search strategy, including all identified keywords and index terms, will be adapted for each included database and/or information source and will be modified as the research team becomes familiar with the evidence base. The reference list of all included sources of evidence will be screened and relevant experts will be consulted to identify any additional studies.

Studies published in languages other than English will be assessed using the intervention description outlined in the abstract and recorded as potentially eligible. However, due to research capacity limitations, only studies reported in English will be included in the analysis. To maximise the scope of this review, there will be no time limits imposed on the searches or included studies.

The databases to be searched are MEDLINE, Embase, PubMed, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials. Sources of unpublished studies and grey literature to be searched are Eldis, Global Health (CAB Direct), Global Index Medicus (WHO), International Initiative for Impact Evaluation (3ie), COnnecting REpositories (CORE) and Google Scholar. All searches undertaken will be documented clearly with the search strategy, date and the number of results found.

Source of evidence selection

Following the search, all identified citations will be collated and uploaded into Covidence systematic review software 2022 (Veritas Health Innovation, Melbourne, Australia) and duplicates removed. Titles and abstracts will then be screened by one reviewer for assessment against the inclusion criteria for the review. Potentially relevant sources will be retrieved in full, and their citation details imported into the reference management software Endnote V.20 (Clarivate, 2013). The full text of selected citations will be assessed in detail against the inclusion criteria by one reviewer. We will record and report all reasons for exclusion at full text according to the defined inclusion criteria. Any uncertainties that arise at each stage of the selection process will be resolved through discussion between the primary reviewer and an additional reviewer/s.

Data extraction

Data will be extracted from included papers by one reviewer using a data extraction tool developed by the review team (table 1), adapted from the JBI template for data extraction.³¹ A random sample of 5% of included studies will additionally be reviewed by the senior author. Extracted data will include details of the study characteristics, intervention and evaluation. The purpose of each intervention component will be categorised based on the definitions outlined in the Evidence Review of Multicomponent interventions to increase vaccine uptake by the National Institute for Health and Care Excellence²³ and the ‘Communicate to Vaccinate’ taxonomy of communication interventions for childhood vaccination.³⁸

Table 1.

Data extraction tool

Dimensions	Components	Details as applicable
General information	Authors
	Year	Any year
	Country/countries of study	Studies with data from LMICs will be included
	Language	Studies in all languages will be documented; only English language studies will undergo full-data extraction and analysis
	Vaccine(s)	All vaccines will be included
Study characteristics	Study design
	Study setting	Community, healthcare or educational
	Target population of the vaccine	Children <5, newborns, children <1
	Target population of the intervention	Parents/carers, pregnant women, health workers
	Study participants	Number, age, sex
Intervention	Intervention description	Overview of what the intervention involves
	Number of components
	Purpose	Inform or educate: Interventions to enable people to understand the meaning and relevance of vaccination to their health and the health of their family or community. Remind or recall: Interventions to remind consumers or providers of required vaccinations and to recall those who are overdue. Teach skills: Interventions to provide individuals with the ability to operationalise knowledge through the adoption of practicable skills. Provide support: Interventions to assist people in addressing specific challenges to vaccination that arise within their day-to-day lives. Facilitate decision making: Interventions that extend beyond informing or educating by presenting all options related to vaccination decision-making in an unbiased and impartial manner. Enable communication: Interventions that explicitly and purposefully aim to bridge a communication gap/make communication possible with particular people or groups. Enhance community ownership: Interventions to increase community participation and promote interaction between the community and health services. Increase acceptability: Interventions that make vaccinations more acceptable to people such as alterative settings, providers or vaccine formulations. Improve access: Interventions that make it easier for people to access vaccination including outreach services, extended clinic hours and integrated services. Improve infrastructure: Interventions targeting processes, staffing and settings such as booking systems, incentives, mandatory vaccination and audits and feedback to providers on uptake rates.
	Format/method of delivery	Eg, pamphlets, outreach services, media campaigns, decision aids, incentives
	Reported effectiveness	Change in vaccine uptake or coverage as reported by the authors
Evaluation methods	Programme theory or theory of change	If described
	Evaluation framework	Eg, RE-AIM framework, realist evaluation, MRC guidance on complex interventions
	Methods	Including study design, data collection methods, data analysis and dissemination
	Outcomes	Primary and secondary outcomes
	Timing of outcomes	Details on when the outcomes were measured in relation to implementation
	Effectiveness	As reported in the source of evidence
	Strengths and limitations of evaluation methods	Practicability: How well can the evaluation methods achieve the desired objectives within the available time and resource constraints? Applicability: How well do the methods allow the results to be generalised more broadly? Sensitivity: How well suited are the methods for identifying the effectiveness of the intervention in this context? Specificity: How well do the methods identify interventions that will not be effective at improving vaccine uptake in this context?

LMICs, low and middle-income countries; MRC, Medical Research Council; RE-AIM, Reach, Effectiveness, Adoption, Implementation, Maintenance.

The data extraction tool will be piloted, modified and revised as necessary during the process of extracting data from each included evidence source. Categories will be modified and refined during the review process as new potentially relevant terms and concepts are revealed.³³ Any uncertainties will be resolved through discussion between the reviewer and the two senior researchers. If appropriate, authors of papers will be contacted to request missing or additional data.

Data analysis and presentation

We will report the results of the search and the study inclusion process in full using a PRISMA-ScR flow diagram.³⁴ A brief description of the studies will also be included, using descriptive statistics to summarise the most common study settings, participant groups, vaccines and intervention component number, types and combinations. A map of the geographic distribution of the identified studies will be included.

We will present key aspects of the multicomponent interventions from the included studies in tables, separated by intervention setting (healthcare, community or educational). Frequencies, distribution and a heat map will also be used to graphically depict what intervention types are being combined, in what settings, with what vaccine and with which target populations. We will present data on the reported effectiveness of each study as described by the authors.

To assess the strengths and limitations of the evaluation methods (including study design, data collection methods, data analysis and dissemination), we will use an adaptation of the PASS criteria developed by Michie et al to evaluate methods of behaviour change theory (practicability, applicability, sensitivity and specificity).³⁹ We will present the evaluation methods used for each study in a table and may also include a scoping map of the evaluation frameworks and methods used for each multicomponent intervention.

Patient and public involvement

None.

Ethics and dissemination

Ethics approval is not required for this scoping review. Data will only be obtained from existing sources and no primary data will be generated.

This scoping review forms part of the evidence synthesis phase of the doctoral research project of the lead author (YM). The findings from this scoping review will be presented at relevant conferences, published in a peer-reviewed journal and disseminated through other platforms as appropriate.

Ethics statements

Patient consent for publication

Not applicable.