Original Research

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies

February 1, 2022

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, the research team conducted a megastudy which randomly assigned over 680,000 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to either nudge flu vaccination or to provide a standard-of-care control condition that received no messages. Reminder text messages increased pharmacy vaccination rates by 6.8% over a three-month follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered three days apart and communicated to patients that a vaccine was “waiting for you.” Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy.