Department of Political Science, University of California, Davis, Davis, California, United States of America.
Division of Politics & Economics, Claremont Graduate University, Claremont, California, United States of America.
PLoS One. 2022 Sep 28;17(9):e0274374. doi: 10.1371/journal.pone.0274374. eCollection 2022.
Vaccines are the most effective means at combating sickness and death caused by COVID-19. Yet, there are significant populations within the United States who are vaccine-hesitant, some due to ideological or pseudo-scientific motivations, others due to significant perceived and real costs from vaccination. Given this vaccine hesitancy, twenty state governors from May 12th to July 21st 2021 implemented some form of vaccination lottery aiming to increase low vaccination rates. In the aftermath of these programs, however, the critical question of whether these lotteries had a direct effect on vaccination remains. Previous literature on financial incentives for public health behaviors is consistent: Financial incentives significantly increase incentivized behaviors. Yet, work done specifically on state vaccine lotteries is both limited in scope and mixed in its conclusions. To help fill this gap in the literature, we use synthetic control methods to analyze all 20 states and causally identify, for eighteen states, the effects of their lotteries on both first-dose and complete vaccination rates. Within those eighteen states, we find strong evidence that all but three states' lotteries had positive effects on first-dose vaccination. We find for complete vaccinations, however, over half the states analyzed had negative or null effects. We explore possibilities related to these mixed results including the states' overall partisanship, vaccine hesitancy, and the size of their lotteries finding null effects for each of these explanations. Therefore, we conclude that the design of these programs is likely to blame: Every state lottery only incentivized first-doses with no additional or contingent incentive based on a second dose. Our findings suggest that the design of financial incentives is critical to their success, or failure, but generally, these programs can induce an uptake in vaccination across diverse demographic, ideological, and geographic contexts in the United States.
疫苗是应对 COVID-19 导致的疾病和死亡的最有效手段。然而，美国仍有相当一部分人对接种疫苗持犹豫态度，有些人是出于意识形态或伪科学的动机，有些人则是因为接种疫苗带来了明显的感知和实际成本。鉴于这种疫苗犹豫情绪，2021 年 5 月 12 日至 7 月 21 日，20 位州长实施了某种形式的疫苗接种抽奖活动，旨在提高低接种率。然而，在这些项目实施之后，一个关键问题仍然存在，即这些抽奖活动是否对疫苗接种有直接影响。关于公共卫生行为的经济激励措施的先前文献是一致的：经济激励措施显著增加了受激励的行为。然而，专门针对州疫苗抽奖的研究工作在范围上有限，结论也不一致。为了帮助填补这一文献空白，我们使用综合控制方法分析了所有 20 个州，并在因果关系上确定了其中 18 个州的抽奖活动对第一剂和完全接种疫苗率的影响。在这 18 个州中，我们有强有力的证据表明，除了三个州之外，所有州的抽奖活动对第一剂疫苗接种都有积极影响。然而，对于完全接种疫苗，我们分析的一半以上的州都有负面或无效的效果。我们探讨了与这些混合结果相关的可能性，包括各州的总体党派性、疫苗犹豫情绪以及抽奖活动的规模，发现这些解释都没有效果。因此，我们的结论是，这些计划的设计可能是罪魁祸首：每个州的抽奖活动都只激励第一剂接种，没有基于第二剂的额外或附带激励。我们的研究结果表明，经济激励措施的设计对其成功或失败至关重要，但总的来说，这些项目可以在美国不同的人口统计学、意识形态和地理背景下，促使人们接种疫苗。
