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Pennsylvania tops 1,500 measles cases as the U.S. could lose its measles elimination status this week

Leaders from the Pan American Health Organization, which is part of the World Health Organization, are meeting this week to decide if measles can still be called eliminated in the U.S.

Two doses of the measles, mumps and rubella (MMR) vaccine has proven 97% effective at preventing disease.
Two doses of the measles, mumps and rubella (MMR) vaccine has proven 97% effective at preventing disease. Read moreKriston Jae Bethel / For the Inquirer

Pennsylvania topped 1,500 reported measles cases on Monday, even as the largest outbreak the country has seen in three decades shows signs of slowing.

The latest milestone comes as international health leaders from the Pan American Health Organization are expected to decide later this week whether the United States will retain its measles elimination status, which it has held since 2000.

Losing the largely symbolic designation from the World Health Organization would indicate that measles — a vaccine-preventable disease — is once again spreading widely in communities across the United States.

Nationally this year, 5,182 measles cases had been reported as of last Thursday — more than twice the total number in all of 2025, according to the Centers for Disease Control and Prevention.

The vast majority of those cases, spread across 47 states and cities, were seen among people who were unvaccinated and contracted the virus from someone else in their community. A total of 18 cases involved international visitors, according to the CDC.

In Pennsylvania, the health department reported 73 new cases in the last seven days, including a rare “breakthrough” case in an individual who was vaccinated.

State officials have confirmed six measles-associated deaths, the most seen in the nation in more than three decades, and are investigating a seventh reported in Franklin County.

Pennsylvania’s outbreak is centered in Lancaster County, right outside the Philadelphia region, and measles is actively spreading in suburban Chester County. The widening outbreak has affected more than half of Pennsylvania’s 67 counties.

Measles is resurging amid declining vaccination rates in the state and nation. Scientists say that about 95% of a community should be vaccinated to prevent spread.

In the Philadelphia region, at least 40% of kindergartens were vulnerable to an outbreak as of last school year, up from 33% the prior year, according to an Inquirer analysis of school immunization data widely used to assess community protection levels.

Two doses of the measles, mumps, and rubella vaccine have proven 97% effective at preventing the disease. So-called breakthrough infections occur in about three out of every 100 cases, and become more likely as the virus becomes more widespread.

Measles is among the most contagious viruses. Nine in 10 unvaccinated people exposed to measles will acquire the disease.