Description of included studies and reported outcomes
| Study, publication status | Study location and setting | Study population | Intervention description | Study methods | Study outcomes |
| Bangure et al, 2015, published46 | Zimbabwe Urban | Mothers or caregivers who recently delivered or during third or seventh day visit in Kadoma City Clinic in Mashonaland West province. Children <7 days | One-way SMS reminders sent 7 days, 3 days and 1 day before immunisation appointment | Study design: RCT Sample size: 304 children (intervention: 152; control: 152) Length of follow-up: 3 months | Receipt of DPT-3 vaccines (coverage) and delay in immunisation (timeliness) |
| Ceballos et al, 2020, published47 | Guatemala Rural | Households with children less than 2 years old and pregnant women, have access to a cellphone, and have at least one literate member in the municipalities of Santa Maria Nebaj and San Miguel Uspantan. 1162 households were randomised into two groups: 610 received SMS reminders (intervention) and 552 did not (control) | One-way SMS reminders sent to the intervention group about a week in advance to the date in which the child was due to receive vaccination | Study design: cluster RCT Sample size: 658 children (intervention: 340; control: 318) Length of follow-up: 6 months | Receipt of routine vaccines (coverage) |
| Coleman et al, 2020, published56 | South Africa Urban | Mothers–child pairs receiving ANC and PNC/EPI care in six public healthcare facilities in the Mobile Alliance for Maternal Action (MAMA) intervention in inner city Johannesburg. Children <12 months | One-way maternal health SMS reminders sent twice weekly for each vaccination in the first year | Study design: non-RCT Sample size: 356 children (intervention: 181; control: 175) Length of follow-up: 12 months | Receipt of first-year infant vaccines (coverage) |
| Dipeolu et al, 2017, unpublished PhD thesis57 | Nigeria Rural | Mothers–child pairs that delivered and mothers attending immunisation clinic at 10 primary healthcare facilities in Kajola and Ibarapa North LGA in Oyo State. Children <4 weeks. | One-way SMS reminders sent 2 days, 1 day before and on the day of immunisation appointment | Study design: non-RCT Sample size: 366 children (intervention: 179; control: 187) Length of follow-up: 6 months | Receipt of all infant vaccines (coverage) |
| Dissieka et al, 2019, published58 | Cote d’Ivoire Mixed (includes rural, urban and peri-urban locations) | Mothers–child pairs recruited at time of BCG immunisation visit in 29 health facilities in Korhogo district, Children <5 weeks | One-way SMS reminders sent 2 days before immunisation appointment | Study design: RCT Sample size: 1596 children (intervention: 798; control: 798) Length of follow-up: 12 months | Receipt of all infant vaccines (coverage) |
| Domek et al, 2016, published59 | Guatemala Urban | Parents–child pairs who owned a mobile phone and brought their children for vaccination at two public health clinics in Guatemala City clinics. Children aged between 8 and 14 weeks | One-way SMS reminders sent at 6, 4 and 2 days before the next scheduled immunisation appointment date | Study design: RCT Sample size: 321 children (intervention: 160; control: 161) Length of follow-up: 10 weeks | Receipt of DPT-3 vaccines (coverage) |
| Domek et al, 2019, published60 | Guatemala Mixed (includes rural and urban locations) | Parents–child pairs who owned an active phone capable of receiving SMS who brought their children at two clinics in urban Guatemala City and two clinics in rural southwest region (Colomba & Coatepeque, and Quetzaltenango). Children aged between 6 weeks and 6 months | Automated one-way SMS reminders sent at 3 days, 2 days and 1 day before the next scheduled immunisation day | Study design: RCT Sample size: 720 children (intervention: 358; control: 362) Length of follow-up: 10 weeks | Receipt of DPT-3 vaccines (coverage) and timely receipt (timeliness) |
| Ekhaguere et al, 2019, published61 | Nigeria Urban | Parturient mother–child pairs in Mother & Child Hospital Ondo and Akure, Ondo State. Newborn infant | One-way SMS reminders sent 2 days and 1 day before immunisation appointment | Study design: RCT Sample size: 600 children (intervention: 300; control: 300) Length of follow-up: 12 months | Receipt of all infant vaccines (coverage) and timely receipt (timeliness) |
| Eze et al, 2015, published62 | Nigeria Urban | Caregiver–child pairs in eight health facilities in Egor LGA, Edo State Children due for first or second schedule of vaccines | One-way SMS reminders sent 1 day before immunisation appointment. Follow-up messages were sent in cases of missed appointments | Study design: RCT Sample size: 1001 children (intervention: 501; control: 500) Length of follow-up: 18 weeks | Receipt of infant vaccines (coverage) and timely receipt of vaccines (timeliness) |
| Gibson et al, 2017, published63 | Kenya Rural | Mother–child pairs in 76 randomly assigned villages in Gem or Asembo districts. Children less than 35 days old | One-way SMS reminders sent 3 days and 1 day before immunisation appointment* | Study design: cluster-RCT Sample size: 748 children (intervention: 388; control: 360) Length of follow-up: 12 months | Receipt of infant vaccines (coverage) and timely receipt of vaccines (timeliness) |
| Haji et al, 2016, published48 | Kenya Mixed (includes rural and urban locations) | Mother–child pairs in Langata, Machakos and Njoro districts. Children <6 weeks | One-way SMS reminders sent 2 days before and on the day of scheduled immunisation day* | Study design: RCT Sample size: 744 children (intervention: 372; control: 372) Length of follow-up: 14 weeks | Receipt of Penta-3 vaccines (coverage) and timely receipt (timeliness) |
| Kawakatsu et al, 2020, published49 | Nigeria Urban | Caregiver–child pairs attending immunisation clinic at 33 primary healthcare centres (PHCs) across 20 LGAs in Lagos State between 25 March and 27 June 2019. Children <6 weeks | One-way SMS reminders sent 2 days before the scheduled immunisation day | Study design: RCT Sample size: 8337 children (intervention: 4893; control: 3444) Length of follow-up: 3 months | Receipt of all infant vaccines (coverage) and timely receipt (timeliness) |
| Kazi et al, 2018, published50 | Pakistan Urban | Parents–child pairs who owned an active phone in Ibrahim Haidry (IH) union council in Karachi. Children less than 2 weeks of age | Four one-way SMS reminders sent within the week of the scheduled routine immunisation day | Study design: RCT Sample size: 300 children (intervention: 150; control: 150) Length of follow-up: 4 months | Receipt of DPT-3 vaccines (coverage) |
| Nguyen et al, 2017, published51 | Vietnam Rural | Two cohorts include all children born in September and October 2013 (control) and in September and October 2014 (intervention) in Ben Tre province | Multiple one-way SMS reminders sent before the scheduled routine immunisation day | Study design: non-RCT (pre-post intervention design) Sample size: 8075 children (intervention: 4078; control: 3997) Length of follow-up: 12 months | Receipt of infant vaccines (coverage) |
| Oladepo et al, 2020, published52 | Nigeria Rural | Mother–child pairs attending immunisation clinics in Primary Health Centres in 14 LGAs across six states and the Federal Capital Territory (FCT), Abuja. Children ≤2 months | Multiple one-way SMS reminders sent three times a week before the next immunisation appointment | Study design: non-RCT Sample size 3500 children (intervention: 1750; control: 1750) Length of follow-up: 10 months | Receipt of all infant vaccines (coverage) and timely receipt (timeliness) |
| Schlumberger et al, 2015, published53 | Burkina Faso Urban | Mother–child pairs attending Centre de Santé et de Promotion Social (CSPS) in Colma 1 (medical district of Do). Do is one of the urban regions in Bobo-Dioulasso, Burkina Faso. Children <1 month | One-way SMS reminder sent before next due EPI vaccination sessions | Study design: RCT Sample size: 523 children (intervention: 255; control: 268) Length of follow-up: 5 months | Receipt of DPT-3 vaccines (coverage) and timely receipt (timeliness) |
| Seth et al, 2018, published54 | India Rural | Pregnant mothers and children less 24 months in rural community in Mewat region in Haryana State from 10 July 2016 and 20 July 2017 were prospectively enrolled. | One-way SMS reminders sent before day of scheduled immunisation day* | Study design: RCT Sample size: 405 children (intervention: 201; control: 204) Length of follow-up: 13 months | Receipt of all infant vaccines (coverage) and timely receipt (timeliness) |
| Uddin et al, 2016, published55 | Bangladesh Rural (A) and urban (B)† | Pregnant women and children aged less than 11 months in two separate areas. Rural: two upazilas (sub-districts) in Sunamgonj district. Urban: two zones in Dhaka City with the most street dwellers | Three one-way SMS reminders sent 1 day before scheduled EPI immunisation day, at the opening time on the day of the scheduled EPI immunisation, and 2 hours before closing time on the day of the scheduled EPI immunisation day | Study design: non-RCT (pre-post intervention design) Rural: Sample size: 2080 children (intervention: 1040; control: 1040) Urban: Sample size: 2078 children (intervention: 1038; control: 1040) Length of follow-up: 12 months | Receipt of infant vaccines (coverage) |
*Multi-arm trial includes other interventions not relevant to this study.
†Study reported separate quasi-experiment data for urban and rural settings.
ANC, Antenatal care; DPT-3, third dose of diphtheria, pertussis and tetanus; EPI, Expanded Programme on Immunization; LMICs, low/middle-income countries; PNC, Postnatal care; RCT, randomised controlled trial; SMS, short message service.