Lauren Gardner, director of the Center for Systems Science and Engineering at Johns Hopkins, expressed hope that the findings would raise awareness about the critical need for vaccinations and the necessity to address declining rates.

Gardner emphasized the importance of analyzing vaccination rates at the county level to understand community risk for measles outbreaks, despite state averages appearing healthy.

Only four states—California, Connecticut, Maine, and New York—showed increases in median county-level vaccination rates, likely due to their laws prohibiting non-medical exemptions for school immunizations.

A recent report from Johns Hopkins University reveals alarming declines in childhood vaccination rates across the U.S., with 78% of the 2,066 counties studied reporting decreases in measles, mumps, and rubella (MMR) vaccination rates from an average of nearly 94% pre-pandemic to about 91% post-pandemic.

The study highlights significant variations in vaccination rates within states, indicating that while some states may report healthy averages, specific counties may be at greater risk for outbreaks due to low coverage.

Despite measles being declared eliminated in the U.S. in 2000, the recent decline in vaccination rates raises concerns about the disease potentially becoming endemic again, especially as the CDC reported over 1,000 confirmed measles cases, the highest in over 30 years.

As of late May 2025, the U.S. has seen 1,088 confirmed measles cases across 32 states, marking the first time in five years that cases have surpassed the 1,000 mark, with three measles-related deaths reported this year, all involving unvaccinated individuals.

Experts attribute the declining vaccination rates to rising vaccine hesitancy among parents, fueled by perceived low risk due to the historical near-elimination of measles and safety concerns.

Healthcare providers are urged to engage with vaccine-hesitant parents, addressing their concerns and emphasizing the importance of vaccinations in disease prevention.

The CDC recommends two doses of the MMR vaccine, with the first dose given between 12 to 15 months and the second between 4 and 6 years, achieving 93% and 97% efficacy against measles, respectively.

The current decline in vaccination rates moves further away from the 95% herd immunity threshold necessary to limit the spread of measles, increasing the risk of outbreaks.

The study utilized a novel county-level dataset to identify vaccination trends and areas at greater risk for outbreaks due to low coverage, complementing existing state and national data from the CDC.