Behavioral nudges increase COVID-19 vaccinations: Two randomized controlled trials

Dai, H.; Saccardo, S.; Han, M. A.; Roh, L.; Raja, N.; Vangala, S.; Modi, H.; Pandya, S.; Croymans, D. M.

Fighting the COVID-19 pandemic requires quick and effective strategies to maximize vaccine uptake. We present two sequential randomized controlled trials (RCTs) that tackle this challenge with behavioral science insights. We deliver text-based nudges to UCLA Health patients one day (first RCT; N=113,229) and eight days (second RCT; N=90,662) after they receive notifications of vaccine eligibility. In the first RCT, text messages designed to make vaccination salient and easy to schedule boost appointment and vaccination rates by 86% and 26%, respectively. Nudges that make patients feel endowed with the vaccine heighten these effects, but addressing vaccine hesitancy via a video-based information intervention does not yield benefits beyond simple text. These results hold across ethnicity and age groups. By contrast, online experiments (N=2,003) soliciting hypothetical responses to the same messages reveal the opposite patterns, underscoring the importance of pilot-testing behavioral nudges in the real world before scaling them up. In the second RCT, we further find that receiving a second reminder boosts appointment and vaccination rates by 52% and 16%, respectively. Our findings suggest that text-based nudges can substantially increase and accelerate COVID-19 vaccinations at almost zero marginal cost, highlighting the promising role of behavioral science in addressing a critical component of the COVID-19 pandemic response.