Four Fully Vaccinated Pennsylvanians Test Positive for Measles Amid Outbreak

Pennsylvania Secretary of Health Dr. Debra Bogen announced Friday that four people who had received two doses of the measles-mumps-rubella (MMR) vaccine tested positive for measles. The cases, involving three adults and one child from Centre, Jefferson, Lancaster and Lycoming counties, did not require hospitalization.

Bogen said breakthrough infections are uncommon, noting that about 3% of measles cases nationwide this year have occurred in fully vaccinated individuals. She added that when such cases do happen, the illness is typically milder, with fewer complications and less transmission than among the unvaccinated.

The outbreak, which began in late April, has produced 676 confirmed cases and 124 hospitalizations in Pennsylvania, with two deaths reported in Lancaster County. More than 99% of cases and all hospitalizations have involved unvaccinated people.

State health officials continue to emphasize that two doses of MMR remain the most effective protection, providing roughly 97% immunity. Since the outbreak started, the Department of Health has organized over 120 pop-up vaccination clinics, delivering nearly 4,300 MMR doses, and the overall number of doses administered this year has risen from about 25,000 to over 46,000 per month.

Bogen urged residents who suspect exposure and exhibit symptoms to contact their health care provider before visiting a clinic, to limit further spread. She also noted that school vaccination rates remain high, with nearly 93% of kindergarteners fully vaccinated, helping to safeguard students and vulnerable community members.