Stanford University


Using Donald Trump’s COVID-19 Vaccine Endorsement to Give Public Health a Shot in the Arm: A Large-Scale Ad Experiment

Brad Larsen
Marc J. Hetherington
Steven H. Greene
Timothy J. Ryan
Rahsaan D. Maxwell
Steven Tadelis

April 2022

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We report a large-scale randomized controlled trial designed to assess whether the partisan cue of a pro-vaccine message from Donald Trump would induce Americans to get COVID-19 vaccines. Our study involved presenting a 27-second advertisement to millions of U.S. YouTube users in October 2021. Results indicate that the campaign increased the number of vaccines in the average treated county by 103. Spread across 1,014 treated counties, the total effect of the campaign was an estimated increase of 104,036 vaccines. The campaign was cost-effective: with an overall budget of about $100,000, the cost to obtain an additional vaccine was about $1 or less.

Stanford University