Table 2

Subgroup analysis of SMS reminders effectiveness on improving childhood immunisation coverage

SubgroupNo of studies*SamplePooled RR95% CII2 statistic (%)P value†
All studies1932 7121.161.10 to 1.2190.4
Country’s income status<0.001
 Low-income country15231.391.19 to 1.62
 Lower middle-income country1430 1341.191.13 to 1.2689.9
 Upper middle-income country420551.010.96 to 1.0658.4
Study design0.060
 Randomized Controlled trials1316 2571.131.06 to 1.2089.6
 Non-randomised controlled trials616 4551.221.12 to 1.3292.2
Study setting0.625
 Rural settings715 8321.111.03 to 1.2092.0
 Mixed settings330601.220.99 to 1.5196.7
 Urban settings913 8201.171.09 to 1.2683.3
Outcome measured0.270
 DPT-3 coverage845131.141.06 to 1.2280.4
 Overall immunisation coverage1128 1991.171.10 to 1.2593.4
Number of SMS reminders sent0.441
 1 or 2 SMS reminders910 6831.151.08 to 1.2289.2
 >2 SMS reminders1022 0291.171.07 to 1.2792.0
Timing of last SMS reminder0.124
 Sent on scheduled immunisation day453071.271.08 to 1.4991.9
 Sent 1 or 2 days before scheduled day1527 4051.131.07 to 1.1989.9
Risk of bias (quality) of included studies<0.001
 Low risk of bias776251.381.22 to 1.5586.7
 Moderate and high risk of bias1225 0871.071.03 to 1.1284.6
  • *Uddin et al, 2020 reported two separate interventions: Uddin, 2020 (A) for rural setting and Uddin 2020 (B) for urban setting.

  • †χ2 test for subgroup difference.

  • DPT-3, third dose of diphtheria, pertussis and tetanus; SMS, short message service.