Pennsylvania measles outbreak grows as low vaccination rates fuel spread

Pennsylvania’s measles outbreak reached 81 confirmed cases as of June 25, with Lancaster County accounting for 38 and Lebanon County for 20, a concentration that shows how quickly pockets of low vaccination coverage can turn into sustained spread. In Lancaster County, that has meant more than a case count: it has meant exposures tied to an Amish and Mennonite region where distrust of vaccination has made containment harder, and to everyday places such as Ephrata Mennonite School and the Lancaster County Courthouse.

The state’s numbers sit inside a larger national surge. The Centers for Disease Control and Prevention said the United States had 2,134 confirmed measles cases in 2026 as of June 25, and 93% were outbreak-associated. The country recorded 2,288 confirmed cases in 2025, the highest annual total in 25 years. Measles was declared eliminated in the United States in 2000, but the CDC says larger outbreaks typically follow importation into close-knit communities with low vaccination coverage.

Pennsylvania’s school data help explain why the virus has found room to move. A Philadelphia Inquirer analysis found that only 17 of the state’s 67 counties had kindergarten vaccination levels high enough to protect against measles as of the 2024-25 school year. The epidemiological benchmark is 95% coverage, the level generally needed to stop community spread. More than 200 schools in Philadelphia, Delaware, Chester, Montgomery, and Bucks counties fell below that threshold, leaving a patchwork of protection across the state.

The Lancaster outbreak has repeatedly been linked to unvaccinated people. On Feb. 3, state health officials reported five measles cases in Lancaster County and said all were unvaccinated. Last year, the Pennsylvania Department of Health warned that an out-of-state visitor who had traveled from Texas tested positive while visiting Lancaster County, and the Lancaster County Health Advisory Council met on April 23, 2025, after the county’s first confirmed case that year. Those episodes underscored how imported infections can spread once they enter communities with low uptake of the MMR vaccine.

Doctors have also warned that adult measles can be especially severe. The CDC says the MMR vaccine is the best protection, and that measles can cause pneumonia, encephalitis and death. The highest risk of serious complications falls on children under 5, adults over 20, pregnant women and people with weakened immune systems. In Lancaster and Lebanon counties, the outbreak has become less about one virus than about what happens when trust in vaccination breaks down before public health can close the gap.