COEP Replication package for "Indoor Vaccine Mandates in U.S. Cities, Vaccination Behavior, and COVID-19 Outcomes"

Many U.S. cities introduced indoor vaccine mandates in 2021–2022 to increase COVID-19 vaccination and curb transmission. While national mandates abroad boosted uptake, the effects of city-level mandates in the U.S. remain unclear. Using the synthetic difference-in-differences methodology, we estimate the impact of mandates in nine major cities on first-dose uptake, cases, and deaths. We find no consistent pattern of significant effects, and results are robust across estimators, outcome definitions, lag structures, and donor pool choice. The contrast with international findings suggests localized mandates may be less effective in settings with high baseline coverage, mobility across jurisdictions, and vaccine hesitancy.

2021至2022年间，美国多个城市推出了室内疫苗强制令（indoor vaccine mandates），以提升新冠疫苗接种率并遏制病毒传播。尽管海外各国的国家级疫苗强制令有效提升了疫苗接种率，但美国市级层面的疫苗强制令所产生的效应仍不明朗。本研究采用合成双重差分法（synthetic difference-in-differences），评估了美国9座主要城市的疫苗强制令对首剂疫苗接种率、新冠感染病例数及死亡数的影响。研究未发现显著效应的一致模式，且结果在不同估计方法、结局指标定义、滞后结构以及供体池（donor pool）选择下均保持稳健。与国际相关研究结果的对比表明，在基线疫苗接种覆盖率较高、跨辖区人员流动频繁且疫苗犹豫程度较高的场景中，地方性疫苗强制令的效果可能相对有限。