Do mobile phone-based reminders and conditional financial transfers improve the timeliness of childhood vaccinations in Tanzania? Study protocol for a quasi-randomized controlled trial

BACKGROUND: Vaccination is a cost-effective strategy for reducing morbidity and mortality among children under 5 years old. To be fully protected from diseases such as tuberculosis, diphtheria, pertussis, and polio, children must receive all recommended vaccinations in a timely manner. In many countries, including Tanzania, high overall vaccination rates mask substantial regional variation in vaccination coverage and low rates of vaccination timeliness. This study evaluates the efficacy of mobile phone-based (mHealth) reminders and incentives for improving vaccination timeliness in the first year of life. METHODS: The study, conducted in Mtwara Region in Tanzania, includes 400 late-stage pregnant women enrolled from rural and urban health facilities and surrounding communities. The primary outcome is timeliness of vaccinations among their children at 6, 10, and 14 weeks after birth. Timeliness is defined as vaccination receipt within 28 days after the vaccination due date. The quasi-randomized controlled trial includes three arms: (1) standard of care (no reminders or incentives), (2) mobile phone-based reminders, and (3) mobile phone-based reminders and incentives in the form of conditional financial transfers. Assignment into study arms is based on scheduled vaccination dates. Reminder messages are sent to arms 2 and 3 participants via mobile phones 1 week and 1 day prior to each scheduled vaccination. For arm 3 participants, reminder messages offer an incentive that is provided in the form of a mobile phone airtime recharge voucher code for each timely vaccination. Vaccination dates are recorded via participant contact with an mHealth system, phone calls with mothers, and a review of government-issued vaccination cards during an end-line survey. Random effects logistic regression models will be used to estimate the effects of reminders and incentives on the timeliness of vaccinations. DISCUSSION: The results will inform implementation science research on the effectiveness of reminders and incentives as a means of improving vaccination timeliness. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03252288. Registered on 17 August 2017 (retrospectively registered). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-019-3430-4) contains supplementary material, which is available to authorized users.