Text-message reminders did not show a clear difference in vaccination
Vaccination was slightly higher among families sent SMS reminders, but the difference was not clear when all randomized families were analyzed.
The key idea
The advantage seen at six weeks depended on whom researchers considered: with all families, the difference could have been due to chance.
The study, in plain language
Three hundred families with a newborn and phone access were randomized into two groups of 150. All received initial vaccine guidance; half were also sent reminders during the weeks of the baby’s three vaccine rounds, at 6, 10, and 14 weeks of age. Researchers compared coverage of scheduled doses and whether babies were up to date at 18 weeks.
When all families were analyzed according to their randomized group, vaccination was slightly higher with the offer of SMS, but the difference could have been due to chance. In a per-protocol analysis that excluded people without complete follow-up, a verified card, or confirmation they received the SMS, a difference appeared at six weeks. Because this excluded some randomized families, that comparison no longer fully preserves randomization. The study also took place at one site, and only 69.3% of cards could be verified.
What they found
- All families received guidance, and half were assigned SMS reminders.
- With all families analyzed as randomized, vaccination was slightly higher with messages, but the difference could have been due to chance.
- The difference at six weeks appeared only in the per-protocol analysis, which excluded some families.
How they studied it
Three hundred families in Karachi were randomized, 150 per group. Everyone received guidance, and half were assigned SMS messages during the weeks of the 6-, 10-, and 14-week doses. Vaccination status was measured at 18 weeks, as was coverage of each scheduled dose.
What the study cannot show
- The trial took place in one community and required phone access and the ability to read SMS. Vaccination status was verified by card for about seven in ten participants; confirmation was unavailable for the rest.
- The study’s power calculation targeted a larger difference than the one observed. The per-protocol analysis adds selection after assignment.
Something to think about
When evaluating a reminder, do you look at everyone who was supposed to receive it or only those who received and read it? These are different questions.
The original study
Effect of Mobile Phone Text Message Reminders on Routine Immunization Uptake in Pakistan: Randomized Controlled Trial
Source under CC BY 4.0. English adaptation and explanation by PaperFlow, with AI assistance. The text has been reorganized for a general audience; it is not the complete paper and does not imply endorsement by its authors.
One study alone does not represent a field's consensus. Educational content does not replace professional advice. Report a possible error.
