Overview
- A peer-reviewed JAMA Pediatrics study published June 1 used a birthday-linked natural experiment to measure vaccine impact in children aged 2 to 5.
- Researchers compared national insurance claims from five non-pandemic seasons and found fall-born children had vaccination rates 8.6 to 12.5 percentage points higher than summer-born peers.
- The analysis shows that for every 100 children vaccinated in this age group there are roughly 9 to 14 fewer flu cases in a season.
- Authors estimate that higher coverage among 2–5-year-olds could prevent hundreds of thousands to about one million U.S. flu cases per season, and the results address an evidence gap cited in recent U.S. policy debates.
- The study is limited to very young children because the birthday visit pattern drives the quasi-random assignment, and its findings arrive as CDC recommendations and public concern over low child vaccination rates and recent child flu deaths are under review.