A new study has found that the measles-mumps-rubella (MMR) vaccination rate among American children has fallen about 3% since the start of the COVID-19 pandemic, aligning with the rise of anti-vaccine misinformation.
The change comes after over a decade of more stable MMR vaccination rates, the study’s senior author, Lauren Gardner, director of Johns Hopkins University’s Center for Systems Science and Engineering, told HuffPost.
The study, published on Monday in JAMA, found that 78% of the 2,066 counties studied experienced a decline in their MMR vaccination rates over the past five years. On average, the rate fell from 93.92% pre-pandemic to 91.26% post-pandemic, marking a 2.67% decline.
Of the 33 states included in the study, only California, Connecticut, Maine and New York reported an increase in the median county-level MMR vaccination rate. The lowest MMR rates observed in the study were in Wisconsin, confirming previous findings.
The shift means the U.S. is “moving further away from the 95% herd immunity threshold to predict or limit the spread of measles,” Johns Hopkins University said with the release of the study.
Though measles was declared eliminated in the U.S. 25 years ago, it’s now surging with more than 1,000 confirmed cases and three confirmed deaths this year in an outbreak largely centered in Texas. Only 3% of those infected are known to have received at least one dose of the MMR vaccine, the Centers for Disease Control and Prevention says.
Even as the outbreak grows, lawmakers in Texas approved a bill earlier this week that would make it much easier for children to enroll in school without the MMR vaccine and other standard inoculations. Since 2018, the Texas Tribune reported, such exemption requests have more than doubled from 45,900 to more than 93,000 in 2024.
The observed downturn in MMR vaccine rates comes as anti-vaccine misinformation thrives online at a rate outpacing the interventions to address it, a study out of Columbia University found last year.
“Misinformation is not new and its noxious consequences are not insurmountable, but its effect on vaccine hesitancy through social media is an urgent global threat to public health,” the study’s lead author, Kai Ruggeri, said upon its release.
Health and Human Services Secretary Robert F. Kennedy Jr., long one of the loudest voices in the anti-vaccine movement, is also a known spreader of misinformation about the MMR shots.
In an April interview with CBS, he claimed the vaccine “wanes very quickly,” even though evidence shows it lasts most people their entire lifetimes. And in a March appearance on Fox Nation, he pushed baseless claims that Vitamin A could be a treatment for measles. He also falsely claimed that “a lot of studies” show that natural immunity derived from catching measles can help the immune system fight cancer, cardiac disease and allergies.