SMS Text Message Reminders to Improve Infant Vaccination Coverage in Guatemala: A Pilot Randomized Controlled Trial

Motivated by the belief that mobile technologies, such as short message service (SMS) texts, have potential for low-cost disease management in low- and middle-income countries (LMICs), these researchers sought to determine if an SMS-based vaccination reminder system aimed at improving completion of the infant primary immunisation series would be feasible and acceptable in Guatemala.

As reported here, 2008-2009 data show that only 75% of infants received the recommended 3 doses of pentavalent vaccine (diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae B) by age 12 months in the central Department of Guatemala (which includes Guatemala City). In response, an SMS reminder platform was developed by the Guatemala Ministry of Public Health and Social Assistance (Ministerio de Salud Pública y Asistencia Social, MSPAS), the Pan American Health Organization (PAHO), and project Optimize to deliver SMS messages to health care workers. In collaboration with the MSPAS and PAHO, this platform was modified in the current study to provide SMS reminders to parents.

This evaluation was designed as a pilot randomised controlled trial and was conducted at 2 public health clinics in Guatemala City serving a publically insured and low-income population. Enrollment occurred between March and April of 2013. Parents over the age of 18 with infants between the ages of 8 and 14 weeks presenting for the first dose of the 3-dose infant primary immunisation series were eligible if they owned a mobile phone with SMS text messaging capability. At least one parent had to be literate and able to use SMS technology. Participants were allocated to either an intervention or usual care group using a computer-generated randomisation scheme, with the investigators being blind to the allocation.

All patients, including usual care patients, received written reminders in the child's immunisation card for the next dose of vaccines at the time of each vaccination. Those randomised into the intervention group also received the following SMS text messages at 6, 4, and 2 days before the next scheduled date for visits 2 and 3: "Your child [autopopulate child's name] is due on [autopopulate date] at [autopopulate clinic name] for vaccines." The SMS messages had a third grade Flesch-Kincaid readability level and were translated into Spanish. All children were followed for 6 months, which allowed 2 months of observation following each expected visit in the primary immunisation series.

The participation rate was 86.8% (321/370); 8 did not own a cell phone and 12 could not use SMS. 96.9% of intervention parents were sent at least one SMS reminder prior to visit 2 and 96.3% prior to visit 3. Both intervention and usual care participants had high rates of vaccine and visit completion, with a non-statistically significant higher percentage of children in the intervention completing both visit 2 (95.0% vs. 90.1%, p = .12) and visit 3 (84.4% vs. 80.7%, p = .69).

Of those in the intervention, 78.3% remembered receiving SMS messages. In general, intervention parents had more favourable views toward SMS reminders than those in the usual care group. More intervention vs. usual care parents agreed that SMS reminders would be helpful for remembering appointments (p < .0001), agreed to being interested in receiving future SMS reminders (p < .0001), and said they would be willing to pay for future SMS reminders (p = .01). All intervention parents would recommend SMS reminders to family.

In short, the "results from this pilot evaluation demonstrated that it was feasible and acceptable for parents to use an SMS-based vaccine reminder system in a LMIC, such as Guatemala, with high user satisfaction."

The researchers outline some lessons learned that could help inform future large-scale randomised trials in LMICs. For example, they suggest having a back-up server and potentially a generator with a detailed protocol to resend messages after outages. Furthermore, other studies have implemented bi-directional messaging into their automated SMS delivery programmes to allow recipients to confirm receipt of a message. This was not implemented in the current study because, while participants could receive an SMS text without charge, they would have had to pay to send a confirmation message. This is an area that could be explored in future studies. "It will also be important in the future to demonstrate test message implementation linked to an immunization registry in a LMIC."