What is it about?

Cash and prize lotteries were used in 20 US states in 2021 to encourage COVID-19 vaccinations. Using an advanced methodology, we find that lotteries increased first-dose vaccination rates but had mixed effects for full vaccination rates. We conclude that this was likely a result of entry to the lotteries only being linked to receiving the first dose of a vaccine.

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Why is it important?

We examine all 20 states that implemented COVID-19 vaccination lotteries using a method that enables causal identification of the effects of these programs. This research is critical to understanding if government lotteries can lead to positive public health outcomes, particularly in the context of a global pandemic. Our major findings are that lotteries increased first-dose vaccination rates, but had mixed effects for full vaccination rates. Furthermore, the partisanship of a state and the per-capita prize size of lotteries had no discernable relationship with the effect size of these lotteries. Future public health incentive programs must focus on what specific behaviors are incentivized avoid these pitfalls.


While much of the world, particularly the United States, has attempted to move on from COVID-19, better understanding what policies were and were not effective for mitigating the negative effects of COVID is critical for preparing for the next pandemic. Furthermore, given limited resources, it is critical to understand what policies were (in)effective and why. This paper highlights the importance of carefully designing policies to incentivize the specific behaviors needed to increase public health and safety. Without these careful considerations, policies will lead to middling or, even worse, negative effects.

Sam Fuller
University of California Davis

Read the Original

This page is a summary of: Assessing the effectiveness of COVID-19 vaccine lotteries: A cross-state synthetic control methods approach, PLoS ONE, September 2022, PLOS, DOI: 10.1371/journal.pone.0274374.
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