Healthcare Economist December 29, 2025
Clinical trials focus in-sample (direct) effect of vaccines on health outcomes (e.g., decrease in illness, hospitalization, emergency department use, and death). Typically, however, clinical trials do not test whether the vaccines reduce transmission. FDA do not require this as it would be logistically challenging and costly to estimate indirect effects of vaccination within a clinical trial.
A new AEJ Applied Economics paper by Freedman, Sacks, Simon and Wing (2026) aims to estimate both direct and indirect effects. The use a natural experiment framework for differential vaccine eligibility roll-out by age:
Our focal state, Indiana, granted eligibility to health-care workers, first responders, and nursing home residents on December 14, 2020. In contrast to most states, however, subsequent eligibility groups in...
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