Milkman, K.L.Gandhi, L.Patel, M.S.Graci, H.N.Gromet, D.M.Ho, H.Kay, J.S.Lee, T.W.Rothschild, J.Bogard, J.E.Brody, I.Chabris, C.F.Chang, E.Chapman, G.B.Dannals, J.E.Goldstein, N.J.Goren, A.Hershfield, H.Hirsch, A.Hmurovic, J.Horn, S.Karlan, D.S.Kristal, A.S.Lamberton, C.Meyer, M.N.Oakes, A.H.Schweitzer, M.E.Shermohammed, M.Talloen, J.Warren, C.Whillans, A.Yadav, K.N.Zlatev, J.J.Berman, R.Evans, C.N.Ladhania, R.Ludwig, J.Mazar, NinaMullainathan, S.Snider, C.K.Spiess, J.Tsukayama, E.Ungar, L.Van den Bulte, C.Volpp, K.G.Duckworth, A.L.2022-04-252022-04-252022-02-08K.L. Milkman, L. Gandhi, M.S. Patel, H.N. Graci, D.M. Gromet, H. Ho, J.S. Kay, T.W. Lee, J. Rothschild, J.E. Bogard, I. Brody, C.F. Chabris, E. Chang, G.B. Chapman, J.E. Dannals, N.J. Goldstein, A. Goren, H. Hershfield, A. Hirsch, J. Hmurovic, S. Horn, D.S. Karlan, A.S. Kristal, C. Lamberton, M.N. Meyer, A.H. Oakes, M.E. Schweitzer, M. Shermohammed, J. Talloen, C. Warren, A. Whillans, K.N. Yadav, J.J. Zlatev, R. Berman, C.N. Evans, R. Ladhania, J. Ludwig, N. Mazar, S. Mullainathan, C.K. Snider, J. Spiess, E. Tsukayama, L. Ungar, C. Van den Bulte, K.G. Volpp, A.L. Duckworth. 2022. "A 680,000-person megastudy of nudges to encourage vaccination in pharmacies." Proceedings of the National Academy of Sciences, Volume 119, Issue 6, pp. e2115126119 - e2115126119. https://doi.org/10.1073/pnas.21151261190027-84241091-6490https://hdl.handle.net/2144/44284Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo 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 3 d 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.p. e2115126119en-USCopyright © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).https://creativecommons.org/licenses/by-nc-nd/4.0/Article10.1073/pnas.2115126119710004