Table 3

Subgroup analysis of SMS reminders effectiveness on improving childhood immunisation timeliness

SubgroupNo of studiesSamplePooled RR95% CII2 statistic (%)P value*
All studies1225 2571.211.12 to 1.3087.3
Country’s income status0.554
 Low-income country15231.221.01 to 1.47
 Lower middle-income country1024 0141.201.10 to 1.3089.5
 Upper middle-income17201.381.08 to 1.75
Study design0.560
 Randomised controlled trials1013 6821.211.09 to 1.3487.8
 Non-randomised controlled trials211 5751.251.19 to 1.3252.4
Study setting0.604
 Rural412 7281.201.09 to 1.3174.9
 Peri-urban (mixed urban and rural)214641.211.05 to 1.4045.7
 Urban611 0651.321.11 to 1.5892.3
Outcome measured0.259
 DPT-3 coverage741921.321.13 to 1.5491.1
 Overall immunisation coverage521 0651.201.12 to 1.2872.9
Time cut-off for timeliness0.024
 Scheduled vaccination day613 6841.441.19 to 1.7492.5
 1–28 days after scheduled day611 5731.141.08 to 1.2270.5
Number of SMS reminders sent0.040
 1 or 2 SMS reminders820 4331.161.11 to 1.2159.3
 >2 SMS reminders448241.911.18 to 3.0794.9
Timing of last SMS reminder
 Sent 1 or 2 days before scheduled day1024 1081.251.14 to 1.3685.10.228
 Sent on scheduled immunisation day211490.980.68 to 1.4388.3
Risk of bias (quality) of included studies0.071
 Low risk of bias418711.761.14 to 2.7095.2
 Moderate and high risk of bias823 3861.181.11 to 1.2571.3
  • 2 test for subgroup difference.

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