RESUMO
INTRODUCTION: This study examined the effectiveness of mobile phone reminders in improving the completeness and timeliness of childhood immunization. METHOD: We conducted a parallel arm cluster randomized controlled trial in four primary health care facilities in Nigeria. Reminders were sent to eligible participants in the intervention group at specific intervals when their children were scheduled to receive the vaccines administered at the sixth, 10, and 14 weeks after birth. Immunization records of all participants' children were then tracked to assess their immunization status. RESULTS: The immunization status of the intervention (n = 275) and control (n = 261) arms was analyzed. Completeness and timeliness of the vaccine series were significantly higher (p < .001) among children of participants in the intervention (n = 169, 61.5% and n = 138, 50.2%) than those in the control group (n = 35, 13.4% and n = 13, 5%) arm. DISCUSSION: Mobile phone reminders were established to be effective in increasing the completeness and timeliness of childhood immunization.