Looking back, 2025 may be characterized as “the year of measles in North America.” The U.S. has recorded its highest number of measles cases in more than 30 years, although cases have tailed off significantly in the last eight weeks and are only slightly higher than they were in 2019. The current per capita incidence of measles in the U.S. is roughly 4 per 1 million people.

While there is a cyclical component to measles every several years, declining vaccination rates are by far the largest factor in this increase. According to Johns Hopkins University, the average county-level vaccination rate in the U.S. for measles, mumps and rubella declined from 93.9% pre-pandemic to 91.3% post-pandemic, moving further away from the 95% herd immunity threshold necessary to limit the spread of measles

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