Key Takeaway:
- Pennsylvania has surpassed 1,000 measles cases in 2026, with five deaths and nearly 200 hospitalizations in the Pennsylvania measles outbreak.
- The outbreak has spread to 39 of the state’s 67 counties, with Lancaster County reporting the most cases.
- Vaccination remains the strongest protection, as health officials work to contain the state’s largest measles outbreak in decades.
Pennsylvania has confirmed 1,004 measles cases across 39 counties this year, including five deaths and 198 hospitalizations, making it the largest U.S. state outbreak in more than three decades.
Case Count Surges Across Pennsylvania
The Pennsylvania Department of Health reported the milestone Monday, adding 27 cases since Oct. 2. The Pennsylvania measles outbreak, which began in late April, has spread to more than half of the state’s 67 counties.
The state’s five measles-associated deaths are the most reported in a U.S. measles outbreak in more than three decades. Pennsylvania has also reported nearly 200 hospitalizations, with 198 people hospitalized as of Monday.
The outbreak has surpassed recent large outbreaks in South Carolina and Texas. South Carolina recorded 997 cases across 2025 and 2026, while Texas recorded 990 cases in 2025, according to state and federal data.
The Centers for Disease Control and Prevention reported 3,887 confirmed measles cases nationwide as of Oct. 1, including 963 in Pennsylvania. The 2026 national total is already substantially higher than the 2,289 cases recorded in 2025.
Health Officials Track Uneven Spread
Lancaster County has recorded the most cases in Pennsylvania, with 391 as of Monday. Chester County, meanwhile, reported 84 cases and remains the only county in the Philadelphia region with an active spread, according to local health officials.
Dale Weiser, clinical services supervisor for Chester County’s health department, said investigators are facing difficulties reaching people who may have been exposed.
“People don’t answer the phone. People hang up,” Weiser told The Philadelphia Inquirer. He said controlling the Pennsylvania measles outbreak is difficult without cooperation from the community.
State data also show an unusually high share of adult cases. About two-thirds of Pennsylvania’s reported cases have occurred among adults, while roughly 20% of cases have required hospitalization, according to the Inquirer’s review of state data.
Vaccination Remains Key To Containment
The state says four of the 1,004 people with measles were vaccinated, accounting for less than 1% of cases. The MMR vaccine is 97% effective against measles after two doses, according to the Pennsylvania Department of Health.
The CDC says communities generally maintain stronger protection when more than 95% of people are vaccinated. Measles was declared eliminated from the United States in 2000, but outbreaks can occur when the virus reaches communities with pockets of lower vaccination coverage.
Pennsylvania health officials said more than 53,000 MMR doses were administered statewide during September, more than twice the number given during a typical month. State health centers have also provided more than 8,800 MMR doses during 2026.
The health department continues to monitor cases and provide vaccination clinics as the Pennsylvania measles outbreak spreads. Officials say vaccination remains the best protection against measles.
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