Pennsylvania has recorded four measles-related deaths in 2025, after health officials confirmed two additional fatalities involving unvaccinated residents of Jefferson and Mifflin counties. The earlier deaths occurred in Lancaster County and were described as the state's first measles fatalities in 35 years. Health Secretary Dr. Debra Bogen called it the worst outbreak in more than three decades.
The CDC has confirmed 3,294 measles cases nationally, also a 35-year high. Officials stress that the MMR vaccine is roughly 97% effective, yet only 8% of confirmed cases involved people with a known vaccination history. Herd immunity requires about 95% of a community to be vaccinated; last school year, just 92.7% of U.S. kindergartners were vaccinated.
