Yudin 2017.

Study characteristics
Methods	Aim: to evaluate if text message reminders increase the likelihood of receiving the influenza vaccine among pregnant women. Study design: parallel individual RCT Recruitment: women were approached in the waiting room by research personnel who were not part of the clinical care team and were asked if they were interested in enrolling in a study investigating the use of text messages in pregnancy. Women were told the messages would be about health‐related behaviour in pregnancy, but no mention was made of influenza or vaccination at the time of recruitment. Study duration: 4 weeks Study dates: November 2014 (start recruitment) to March 2014 (end recruitment)
Participants	Inclusion criteria: pregnant woman, aged ≥ 18 years, working mobile phone with ability to receive text messages, ability to speak or understand English Sample size (n): 317 (SMS: 153; standard care: 164) Age (mean): intervention: 32.2 (SD 4.5) years; control: 32.4 (SD 4.9) years Sex (female): 100% Country: Canada (high‐income) Setting: hospital‐based antenatal clinic at St Michael's Hospital, which is a women's health ambulatory care clinic in downtown Toronto
Interventions	Intervention: SMS Content: SMS messages reinforcing that the influenza vaccine is recommended for all pregnant women and safe during pregnancy and breastfeeding Frequency and intensity: weekly (2 SMS/week) Control: standard care/no intervention. All women attending the clinic were given a pamphlet containing information about the risks of influenza during pregnancy, the importance of the vaccine for pregnant women, and the fact that the vaccine is safe in pregnancy and breastfeeding. Co‐interventions: all women received usual ANC, including the verbal recommendation for influenza vaccination.
Outcomes	1. Attendance for influenza vaccination; 2. Satisfaction with receiving SMS and opinion on timing and number of SMS received Outcomes reported but not included in the review: Outcome assessment time point: 6 weeks postpartum (1 time point for all outcomes)
Funding/declarations of interest	Funding: St Michael's Hospital Innovation Fund Grant Conflicts of interest: not reported
Notes	Trial ID: NCT02428738 (registered as a case control study)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computerised random number generator.
Allocation concealment (selection bias)	Low risk	Group allocation was assigned using sequentially numbered, sealed, opaque envelopes which were opened at the time of randomisation by study staff.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Women were told the messages would be about health‐related behaviour in pregnancy, but no mention was made of influenza or vaccination at the time of recruitment. Medical and nursing staff caring for the women were blinded to study group allocation and were not involved in any aspects of the study.
Blinding of subjective outcome assessment (detection bias)	Low risk	Self‐reported subjective outcomes among participants who were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The final analysis was based on the actual treatment received and included 281/317 randomised participants. All analyses using ITT groupings were repeated and there were no changes in results when compared to the analyses based on treatment received (data available upon request).
Selective reporting (reporting bias)	Low risk	Outcomes listed in the online trial registration were reported.
Other bias	Unclear risk	No significant baseline differences.

3TC: lamivudine; ANC: antenatal care; ART: antiretroviral therapy; ARV: antiretroviral; BCG: Bacillus Calmette‐Guérin; CHW: community health worker; DPT: diphtheria, pertussis (whooping cough), and tetanus; DTaP: diphtheria, tetanus, and whooping cough (pertussis); EPI: Expanded Programme on Immunisations; HCP: healthcare provider; HCW: healthcare worker; ICC: intracluster correlation coefficient; IQR: interquartile range; ITT: intention to treat; KES: Kenyan shilling; LMIC: low‐ to middle‐income country; n: number of participants; NHS: National Health Service; NP: nurse practitioner; OPV: oral polio vaccine; OR: odds ratio; PCR: polymerase chain reaction; PMTCT: prevention of mother‐to‐child transmission; RCT: randomised controlled trial; SD: standard deviation; SMS: short message service; WHO: World Health Organization; ZDV: zidovudine.