[PNAS] A 680,000-Person Megastudy of Nudges to Encourage Vaccination in Pharmacies

Encouraging vaccination is a pressing policy problem. Nina Mazar, Professor of Marketing, and her colleagues recently conducted a megastudy with 689,693 Walmart pharmacy customers to ascertain whether text-based reminders would encourage pharmacy vaccination and what kinds of messages worked best. They tested 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination. Reminder texts increased vaccination rates by an average of 2.0 percentage points (6.8%) over a business-as-usual control condition. 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 3 days apart and stated that a vaccine was “waiting for you.” Forecasters failed to anticipate that this would be the best-performing treatment, underscoring the value of testing.