Out of 2,066 counties studies, 1,614 counties, or 78%, reported drops in vaccinations. The average county-level vaccination rate fell from 93.92% pre-pandemic to 91.26% post-pandemic—an average decline of 2.67%, moving further away from the 95% herd immunity threshold to predict or limit the spread of measles.

Childhood vaccination rates against measles fell in the years after the COVID-19 pandemic in nearly 80% of the more than 2,000 U.S. counties with available data.