Direct and Indirect Effects of Vaccines: Evidence from COVID-19

• 成果类型: Article
• 署名作者: Freedman, Seth; Sacks, Daniel W.; Simon, Kosali; Wing, Coady
• 署名单位: Indiana University System; Indiana University Bloomington; University of Wisconsin System; University of Wisconsin Madison; Indiana University System; Indiana University Bloomington
• 刊物名称: AMERICAN ECONOMIC JOURNAL-APPLIED ECONOMICS
• ISSN/ISSBN: 1945-7782
• DOI: 10.1257/app.20230717
• 发表日期: 2026
• 关键词: health-care workers; influenza vaccination; selection bias; PRIVATE; trials

摘要

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.