Text Message Reminders for the Second Dose of Influenza Vaccine for Children: An RCT

"Text message vaccine reminders can prompt families to return for a second dose and offer reliable vaccine education to address common barriers..."

Only 40% to 60% of children in the United States (US) who need 2 doses of the influenza vaccine and receive the first get their second. Barriers include gaps in caregiver knowledge of the influenza vaccine schedule and vaccine hesitancy that may persist even after first-dose receipt. Text messaging is a low-cost, scalable, and accessible way to provide vaccine reminders, potentially overcoming vaccination barriers. This paper describes the Flu2Text randomised controlled trial (RCT), which took place over the 2017-2018 and 2018-2019 influenza seasons among 50 pediatric primary care offices across 24 states.

For the study, 2,086 caregiver-child dyads of children 6 months to 8 years in need of a second influenza vaccination that season were individually randomised 1:1 into intervention versus usual care, stratified by age and language within each practice. Caregivers in the intervention arm received personalised, scheduled text messages including (i) reminders about an upcoming second dose and (2) educational information about the importance of a second dose. Messages were automatically sent centrally using a text messaging service on days 14 and 21 postvaccination to alert families about the next needed dose, day 25 just before the end of the minimal interval between doses, day 28 when the dose was due, and day 42, 2 weeks after the due date. The day 21 message was interactive, allowing caregivers to request further information about vaccine side effects, the necessity of the second dose, and/or the importance of timely second dose receipt.

In season 2 (2018 to 2019) only, caregivers randomided to usual care were sent a message upon enrollment with a link to the American Academy of Pediatrics (AAP)'s Ages and Stages Web site as a 1-time attention control. Usual care had variable reminder systems, including no second dose reminders or letter, phone, email or patient portal messages, or a written card provided at the first dose.

Over the 2 seasons, text message reminders increased second dose of influenza vaccine receipt by season end (April 30). Overall, 83.8% of children in the intervention arm received the second dose by season end versus 80.9% in usual care (effect size: adjusted risk difference (ARD) 3.8%; 95% confidence interval [CI] [0.1 to 7.5]). The effect size by season end in the 2018 to 2019 season was similar to that observed in combined analyses across seasons (83.2% versus 80.1% (ARD) 3.8%; 95% CI [−0.4 to 8.1]). Kaplan-Meier analyses also demonstrated that the intervention arm received more timely vaccination through the season.

There was a larger intervention effect for practices that primarily relied on walk-in influenza vaccinations. For these caregivers, the text messages may function as a cue to action to bring their child back for the second dose during the provided walk-in hours. Also, the bilingual intervention (the messages and study materials were professionally translated into Spanish) worked similarly for both English- and Spanish-speaking caregivers.

Thus, in this large-scale trial of primary care pediatric practices across the US, text message reminders were effective in promoting increased and timelier second dose influenza vaccine receipt.

Editor's note: In a companion commentary titled "Personalized Texts Can Boost Receipt of Second Influenza Shot for Young Children", the authors note the importance and increased effectiveness of personalising text messages.