Measles vaccination rates in children have declined in most U.S. counties, study finds

Amid a widespread decline in childhood measles vaccination rates since before the COVID-19 pandemic across the United States, a study published Monday found that coverage can vary substantially within a state.

Looking at county-level data in 33 states, researchers at Johns Hopkins University found that the MMR (measles, mumps and rubella) vaccination rate decreased from 93.92% in the 2017-2018 school year to 91.26% in the 2023-2024 school year. Other states were not included because they had missing vaccination data, the authors of the study said. 

Of the 2,066 counties the study looked at, 78% saw a decline in vaccination rates. Only four of the 33 states — California, Connecticut, Maine and New York — saw an increase in the average county-level vaccination rate, the study found.