Mobile Phone-Delivered Reminders and Incentives to Improve Childhood Immunisation Coverage and Timeliness in Kenya (M-SIMU): A Cluster Randomised Controlled Trial

"The vast majority of caregivers reported receiving at least one SMS reminder or incentive during the study and that these interventions were influential in their decision to vaccinate their child."

The Mobile Solutions for Immunization (M-SIMU) cluster-randomised controlled trial aimed to assess whether short message service (SMS), or text message, reminders, either with or without mobile-money incentives, could improve the proportion of children fully immunised by their first birthday. The rationale behind the study is that, as mobile phone access and ownership continue to become more common worldwide, opportunities exist to leverage mobile-health (mHealth) technologies to target demand-side barriers, such as forgetting vaccination appointments, not knowing the vaccine schedule, or incurring transportation costs, to improve immunisation uptake. SMS reminders are one of the more commonly deployed demand-side mHealth interventions. Another type of demand-generating intervention is the provision of conditional incentives for completing a desired behaviour. In low- and middle-income countries (LMICs), mobile-money systems are frequently used instead of traditional banking systems and allow for the transfer of money through personal mobile phones.

The M-SIMU study was conducted in rural, western Kenya, an area with high prevalence of HIV, tuberculosis, and malaria. Clusters (i.e., villages) were included in the trial if they were located within Gem or Asembo districts and were within the Health and Demographic Surveillance System (HDSS) boundaries. Clusters were excluded if they had ongoing special health programmes or immunisation activities that could bias the study outcomes. Clusters were randomly assigned and evenly allocated to one of four study groups: control, SMS reminders only (SMS only), SMS reminders plus a 75 Kenyan Shillings incentive (KES; SMS plus 75 KES, where 85 KES = USD$1 as of August 2015), and SMS reminders plus a 200 KES incentive (SMS plus 200 KES).

All caregivers received a single text message through the free and open-source RapidSMS platform at enrolment welcoming them to the study. For the 3 intervention groups, SMS reminders were sent 3 days and the day before scheduled immunisation visits at ages 6 weeks, 10 weeks, and 14 weeks for the 3 doses of pentavalent vaccine and age 9 months for measles vaccine. Health facility recorders (HFR) were present at M-SIMU clinics to document immunisation. For immunised children, HFRs sent an SMS with the date of immunisations received and any change in caregiver's phone number to the RapidSMS server. For pentavalent 2 and pentavalent 3 vaccines, their respective due dates were recalculated to be 4 weeks from the texted pentavalent date (interval-appropriate schedule), and reminders were sent accordingly. Children who either went undocumented by the HFR or who did not receive a pentavalent vaccine had reminders sent at 6 weeks, 10 weeks, and 14 weeks.

In addition to receiving SMS reminders, caregivers were sent either 75 KES (group 3) or 200 KES (group 4) to their mobile phone for each timely dose of pentavalent and measles vaccine received, defined as vaccination within 2 weeks of the Expanded Programme on Immunisations (EPI) scheduled date (i.e., pentavalent1 at 6 weeks, pentavalent2 and pentavalent3 4 weeks after the previous pentavalent dose, and measles at 9 months).

The primary outcome was the proportion of fully immunised children by 12 months of age, defined as receiving Bacillus Calmette-Guérin (BCG), 3 doses of polio vaccine, 3 doses of pentavalent vaccine, and measles vaccine. Vaccination coverage at 12 months of age and timely vaccination for pentavalent, polio, and measles vaccines were predetermined as secondary outcomes. Vaccination timeliness was defined as receiving vaccination within 2 weeks of the EPI due date for individual vaccines. A timely fully immunised child was defined as being fully immunised within 2 weeks of the measles EPI due date.

Between October 14 2013 and October 17 2014, researchers enrolled 2,018 caregivers and their infants from 152 villages into these groups: control (n=489), SMS only (n=476), SMS plus 75 KES (n=562), and SMS plus 200 KES (n=491). Overall, 1,375 (86%) of 1,600 children who were successfully followed up achieved the primary outcome, full immunisation by 12 months of age (296 [82%] of 360 control participants, 332 [86%] of 388 SMS only participants, 383 [86%] of 446 SMS plus 75 KES participants, and 364 [90%] of 406 SMS plus 200 KES participants). Children in the SMS plus 200 KES group were significantly more likely to achieve full immunisation at 12 months of age (relative risk (RR) 1.09, 95% confidence interval (CI) 1.02-1.16, p=0.014) than children in the control group.

The secondary outcome of achieving timely full immunisation, defined as being fully immunised within 2 weeks of the measles vaccine EPI due date, was significantly higher in all 3 intervention groups compared with the control group: SMS only (RR 1.18, 95% CI 1.01-1.39, p=0·045), SMS plus 75 KES (1.37, 1.18-1.59, p<0.0001), and SMS plus 200 KES (1.42, 1.23-1.65, p<0.0001).

Among the topics explored in the discussion section of the paper is the fact that this trial was designed and implemented to closely mimic an effectiveness study and with scalability in mind by enrolling caregivers independent of mobile phone ownership. "[W]e were able to observe significant effects of the mobile phone-delivered interventions in a study population comprised equally of those who reported owning or sharing a mobile phone. By enrolling caregivers who shared a mobile phone, it was implicit that caregivers would need to discuss with the phone owner that SMS messages and incentives would need to be relayed from phone owner to intended recipient. More than 90% of enrolled caregivers reported receiving at least one SMS or incentive, as applicable. When combined with our subgroup analyses, this result suggests that the interventions were successfully relayed. The exact nature of this transfer, and whether there were any informal transactional costs in those who received incentives, is not well understood, but future focus group discussions might provide further insight."

In conclusion: "The success of SMS reminders to elicit a behaviour is multifactorial; the content of the message, the type of behaviour being reminded, indirect and direct costs incurred, literacy level, and other contextual factors all being potential explanatory factors....In other resource-constrained settings where immunisation coverage is low, it is likely that SMS reminders, with or without incentives, could raise immunisation timeliness, but additional research is needed."