New Data Shows MMR Vaccinations on the Decline

July 31, 2025

With reported cases of measles in the U.S. the highest in 30 years, a new study finds that fewer children are receiving their measles, mumps, rubella (MMR) vaccines.

A new county-level dataset by Johns Hopkins University, shows a national decline in the MMR vaccination rate among U.S. children since the start of the COVID-19 pandemic.

"This open, high resolution dataset provides a critical resource to explore and better understand the country's vaccination landscape and its implications for the risk of measles spread," said senior author Lauren Gardner, director of Johns Hopkins University's Center for Systems Science and Engineering.

Here are some key takeaways:

• 5-Year decline:  Vaccinations fell in most counties over the past five years, data indicates.
• Widespread decline:  Out of 2,066 counties studied, 1,614 counties (78%) reported drops in vaccinations. The average county-level vaccination rate fell from 93.92 percent pre-pandemic to 91.26 percent post-pandemic—an average decline of 2.67 percent.
• Immunization Goal:  Researchers tell us that 95 percent is the “herd immunity” threshold to predict or limit the spread of measles.
• Pennsylvania-specific:  In Pennsylvania, 61 out of 67 counties saw MMR vaccination rates decline from the 2018–2019 school year to the 2023–2024 school year.
• More children with measles:  More than 1,000 measles cases have been reported this year in the United States. With the exception of 2019, this is the most cases reported in the U.S. in a single year in over three decades, with the vast majority of cases occurring in unvaccinated children.

Read more about the report online.