Importance: Many organizations implemented COVID-19 vaccination requirements during the pandemic, but the best way to increase adherence to these policies is unknown.
Objective: To evaluate if behavioral nudges delivered through text messages could accelerate adherence to a health system's COVID-19 vaccination policy.
Design, setting, and participants: This randomized clinical trial was conducted within Ascension health system from October 11 to November 8, 2021. Participants included health system employees in the Midwest or South US who were not adherent with the vaccination policy 1 month before its deadline. Data were analyzed from November 17, 2021, to February 25, 2022.
Interventions: Participants were randomly assigned to control or to receive a text message intervention that stated a vaccine had been reserved for the participant, with a scheduled date for vaccination within a 2-week period. Participants could reschedule to a different date within the period or upload a copy of their vaccination card. Follow-up text message reminders were sent the day before and the day of the appointment.
Main outcomes and measures: The primary outcome was adherence to the health system's vaccination policy during the 2-week intervention. Secondary outcomes included time to vaccination during a 4-week follow-up period.
Results: The sample included 2000 participants (mean [SD] age, 36.4 [12.3] years; 1724 [86.2%] women), with 1000 participants randomized to the control group and 1000 participants randomized to the intervention group. Overall, there were 164 Hispanic participants (8.2%), 46 non-Hispanic Asian participants (2.3%), 202 non-Hispanic Black participants (10.1%), and 1418 non-Hispanic White participants (70.9%). By the end of the 2-week intervention, 363 participants in the text message nudge group (36.3%) and 318 participants in the control group (31.8%) were adherent with the vaccination policy, representing a significant increase of 4.9 (95% CI, 0.8 to 9.1) percentage points in adjusted analyses comparing the nudge group with the control group (P = .02). Among participants who became adherent by the end of the 4-week follow-up period, the text message nudge significantly reduced time to adherence by a mean of 2.4 (95% CI, 2.1 to 4.7) days (P < .001) and a median of 5.0 (95% CI, 2.5 to 7.7) days (P < .001) compared with the control group. At 4 weeks, overall vaccination adherence was no longer different between groups (control: 477 participants [47.7%]; intervention: 472 participants [47.2%]).
Conclusions and relevance: This randomized clinical trial found that a behavioral nudge delivered through text messages accelerated adherence to a health system's COVID-19 vaccination policy but did change overall adherence by the time of the policy deadline.
Trial registration: ClinicalTrials.gov Identifier: NCT05037201.