Childhood vaccination rates for measles have declined in nearly 80% of U.S. counties studied since the COVID-19 pandemic, raising concerns among health experts as outbreaks spread across several states.
A new study from Johns Hopkins University, published this week in JAMA, analyzed data from more than 2,000 counties in 33 states. The findings show that most areas have seen a drop in kindergarten measles vaccination rates between the pre-pandemic years (2017–2020) and the post-pandemic period (2022–2024).
“The national numbers don’t always reveal what’s happening locally,” said Dr. Lauren Gardner, the study’s senior author and a specialist in infectious disease modeling at Johns Hopkins. “These county-level declines are real, and they’re deeply concerning.”
So far in 2025, the U.S. has recorded 1,088 measles cases, with three deaths. Most infections have occurred among unvaccinated individuals, and the virus continues to spread through both domestic and international travel. If the trend continues, this year could become the worst for measles in the country in more than 30 years.
Measles was declared eliminated in the United States in 2000, thanks to widespread vaccination. The measles, mumps, and rubella (MMR) vaccine remains highly effective, and public schools require two doses before children enter kindergarten. However, the number of students receiving non-medical exemptions from vaccine requirements reached a record high during the 2023–2024 school year.
Experts warn that to prevent measles outbreaks, communities need at least a 95% vaccination rate. The Johns Hopkins study used data from school records, and where kindergarten-specific figures were unavailable, researchers substituted comparable measures to assess overall trends.
The findings highlight the growing risk of vaccine-preventable diseases in the aftermath of the pandemic, as misinformation, disrupted healthcare access, and rising exemption rates continue to impact public health.
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