A MegaStudy of Text-Based Nudges Encouraging Patients to Get Vaccinated at an Upcoming Doctor’s Appointment
Many Americans fail to get life-saving vaccines each year, and the availability of a vaccine for COVID-19 makes the challenge of encouraging vaccination more urgent than ever. We present a large field experiment (N = 47,306) testing 19 nudges delivered to patients via text message and designed to boost adoption of the influenza vaccine. Our findings suggest that text messages sent prior to a primary care visit can boost vaccination rates by an average of 5%. Overall, interventions performed better when they were 1) framed as reminders to get flu shots that were already reserved for the patient and 2) congruent with the sort of communications patients expected to receive from their healthcare provider (i.e., not surprising, casual, or interactive). The best-performing intervention in our study reminded patients twice to get their flu shot at their upcoming doctor’s appointment and indicated it was reserved for them. This successful script could be used as a template for campaigns to encourage the adoption of life-saving vaccines, including against COVID-19.
We partnered with Walmart to test 22 nudges designed to boost vaccination rates in their pharmacies. Nudges were delivered via text message to over 650,000 Walmart pharmacy patients in the fall of 2020 and encouraged patients to visit Walmart for a flu vaccine. We demonstrate that behaviorally informed messages increase pharmacy vaccination rates by an average of 6.7% over a roughly three-month follow-up period. The most effective messages in our field experiment matched the tone of typical pharmacy communications and reminded patients that a flu shot was waiting for them. These insights suggest that carefully crafted messages informed by the results of this study could nudge the adoption of other vaccines for other infectious diseases, including COVID-19.
We present a pre-registered experiment testing the effects of three, high-payoff (up to $50,000) vaccine regret lotteries in Philadelphia. In each drawing, residents of a randomly selected “treatment” zip code received half of the 12 lottery prizes (boosting their chances to 59-98x those of their neighbors). Our quasi-experimental results yield mixed estimates of the benefits of these lotteries for Philadelphia’s overall vaccination rate. Our experimental results, however, offer a causal estimate of the limited return on even high-odds vaccine lotteries. Difference-in-difference regressions estimate the first treated zip code experienced an insignificant 11% jump in vaccinations compared to control zip codes. Pooling results from all three, we do not detect significant benefits from treatment, and our 95% confidence interval bounds the benefits at 9%.
A Field-Tested Messaging Technique to Boost Vaccine Uptake
This summary provides an evidence-based messaging technique to boost the uptake of life-saving vaccines, based on tests of 37 different SMS messages across 700,000+ patients to increase actual flu vaccination rates. This technique could be used to help encourage follow-through for COVID-19 vaccinations as vaccine supply increases.