A new county-level dataset from researchers at Johns Hopkins University shows a nationwide decline in measles, mumps, and rubella (MMR) vaccination rates among U.S. children since the start of the COVID-19 pandemic.
Of the 2,066 counties studied, 1,614 counties (78%) reported a decline in vaccinations, and the average county-level vaccination rate dropped from 93.92% pre-pandemic to 91.26% post-pandemic — an average decrease of 2.67%, moving further away from the 95% herd immunity threshold needed to predict or contain measles outbreaks.
Only four of the 33 states studied — California, Connecticut, Maine, and New York — reported an increase in average county-level vaccination rates.
The data are published today in JAMA.
The data are released after more than a thousand measles cases have been reported in the United States this year. With the exception of 2019, this is the highest number of cases reported in the U.S. in a single year in more than three decades. The vast majority of cases involved unvaccinated children.
“This open, high-resolution dataset is an important resource for exploring and better understanding the nation’s vaccination landscape and its implications for the risk of measles spread,” said lead author Lauren Gardner, director of the Center for Systems Science and Engineering at Johns Hopkins University and an expert in using data and models to better explore disease spread. This work builds on her experience leading data collection for the Johns Hopkins University COVID-19 Dashboard, which was used globally throughout the pandemic.
Gardner created the Johns Hopkins COVID-19 Dashboard, which was used globally to track cases throughout the pandemic.
The county-level vaccination data complement state- and national-level data from the Centers for Disease Control and Prevention and confirm a general decline in MMR vaccination rates in the U.S. post-COVID-19 pandemic. At the same time, they reveal significant heterogeneity in vaccination patterns within and between states.
The team collected county-wide, two-dose MMR vaccination rates for kindergarten children from the websites of the respective state health departments for 2017-2024, where available. The dataset includes at least one year of vaccination data for 2,237 counties in 38 states.
All data are available for download: https://github.com/CSSEGISandData/MMR_data
Authors include: former visiting researcher Ensheng Dong, doctoral student Samee Saiyed, former research fellow Andreas Nearchou, and undergraduate student Yamato Okura, all of Johns Hopkins.
