疫苗的直接和间接效应：来自COVID-19的证据
Direct and Indirect Effects of Vaccines: Evidence from COVID-19
American Economic Journal: Applied Economics · 2025 · [{"name": "Seth Freedman", "affiliation": ["Indiana University"]}, {"name": "Daniel W. Sacks", "affiliation": ["University of Wisconsin–Madison"]}, {"name": "Kosali Simon", "affiliation": ["Institute of Public Affairs"]}, {"name": "Coady Wing", "affiliation": ["Indiana University"]}]
中文摘要
我们估计疫苗的直接与间接有效性，并评估接种者所产生的降低感染的外部性能延伸多远——这是政策决策的一项关键输入。我们的实证策略使用来自单一州的近乎全量微观数据，并利用12岁与11岁儿童获得新冠疫苗接种资格之间六个月的时间差。接种疫苗使病例减少80%，此为直接效应。这种保护会外溢至密切接触者，产生约为直接效应四分之三大小的家庭层面间接效应。然而，间接效应并未延伸至同校学生。我们的研究结果表明，在设计传染病政策时，疫苗覆盖范围是需要重点考虑的重要因素。（JEL D62, H51, H75, I12, I18, J13）
Abstract
We estimate direct and indirect vaccine effectiveness and assess how far the infection-reducing externality extends from the vaccinated, a key input to policy decisions. Our empirical strategy uses nearly universal microdata from a single state and relies on the six-month delay between 12- and 11-year-old COVID vaccine eligibility. Vaccination reduces cases by 80 percent, the direct effect. This protection spills over to close contacts, producing a household-level indirect effect about three-fourths as large as the direct effect. However, indirect effects do not extend to schoolmates. Our results highlight vaccine reach as important to consider when designing policy for infectious disease. (JEL D62, H51, H75, I12, I18, J13)