Pennsylvania has recorded more than 1,000 measles cases in 2026, state health officials said this week, making it the largest single-state outbreak the country has seen in more than three decades. The milestone comes as the United States overall logs its worst year for measles since 1991, nine years before the disease's domestic spread was declared eliminated.
The Pennsylvania Department of Health put the toll at 1,004 confirmed cases, 198 hospitalizations and five deaths, according to reporting from the Associated Press. Nationally, case counts are nearing 3,900 for the year, with large clusters also reported in South Carolina, Texas, Utah and Ohio. The Centers for Disease Control and Prevention says roughly 95% of this year's confirmed U.S. cases involve people who were unvaccinated or whose vaccination status is unknown, and the agency has acknowledged delays in reconciling some Pennsylvania deaths with its national tracking dashboard.
Falling Vaccination Rates at the Root
The outbreak, which began in April west of Philadelphia, has spread to dozens of counties and taken hold where childhood vaccination coverage has slipped below the roughly 95% threshold epidemiologists say is needed to prevent measles from taking off in a community. National kindergarten MMR vaccination fell to about 92.4% during the 2025–26 school year, leaving an estimated 280,000 children without protection, per CDC figures cited in outbreak coverage. In Lancaster County, one of the hardest-hit areas and home to a large Amish population with historically lower vaccination rates, just under 88% of kindergartners were immunized this school year. Health officials point to a mix of religious and philosophical exemptions — which have roughly tripled over the past decade — and vaccine misinformation as drivers of the gap. Measles remains among the most contagious viruses known: the CDC estimates nine of 10 susceptible people exposed to it will become infected, and the virus can linger in airborne droplets for up to two hours after an infected person leaves a room.
Gov. Josh Shapiro, addressing the state's measles deaths, said: "We hope, and we pray, that those deaths will be the last. This illness and death from measles is completely preventable." Jeffrey Martin, chair of Lancaster General Hospital's Department of Community and Family Medicine, has urged residents to get vaccinated, saying "vaccinations are another way we care for each other." State officials say pop-up clinics and in-home vaccination visits have delivered thousands of additional MMR doses since the outbreak accelerated.
The outbreak now carries international stakes. The World Health Organization's regional office is expected to decide in November whether the United States — and Mexico, which is contending with its own measles clusters — will lose the "measles elimination" status both countries have held since 2000, a designation that requires interrupting the virus's continuous spread for at least a year. Pennsylvania health officials say they expect new cases to keep appearing through the fall as exposures already in the pipeline run their course, even as vaccination clinics continue to expand.
