A measles outbreak centered in south-central Pennsylvania has grown to 84 confirmed cases statewide in 2026, prompting the Pennsylvania Department of Health (DOH) to escalate response efforts including pop-up vaccination clinics, provider education, and new public transparency measures around school-level immunization data.
The majority of cases — 72 of the 84 reported so far this year — are clustered in the Lancaster-Lebanon region, where the outbreak began in late April. Affected counties include Lancaster (41 cases), Lebanon (20), Northumberland (6), Berks (2), Dauphin (2), and York (1). Additional cases identified earlier in the year were reported in Lancaster, Montgomery, and Chester counties. The Shapiro Administration announced the response measures on June 26, 2026, framing vaccination access and provider preparedness as the twin pillars of containment.
Case Distribution Highlights Concentrated Risk
The geographic concentration of cases underscores a pattern seen in measles outbreaks nationally: the virus exploits pockets of under-vaccination to spread rapidly within communities. All confirmed cases in Pennsylvania this year have been among people who are not fully vaccinated. According to the Centers for Disease Control and Prevention, the populations most at risk include unvaccinated individuals, infants too young to have received the measles, mumps, and rubella (MMR) vaccine, and people from regions with low vaccination coverage or active measles circulation.
Measles spreads through airborne transmission when an infected person breathes, coughs, or sneezes, and the virus can remain viable in the air and on surfaces for up to two hours after an infected person has left the area — making it among the most contagious pathogens known. Symptoms, which typically begin seven to 21 days after exposure, include fever, cough, runny nose, red and watery eyes, and a characteristic rash that starts on the head and spreads downward. Without supportive care, measles can cause serious complications and death.
Vaccination Push and Provider Training Underway
In response to the outbreak, DOH state health center staff have administered more than 1,300 MMR vaccine doses statewide in 2026, with over 430 doses delivered through pop-up clinics in the Lancaster-Lebanon region since cases were first identified there in late April. Two doses of the MMR vaccine are 97% effective at preventing infection.
The department has also prioritized clinical preparedness. Because measles was effectively eliminated in the United States as of 2000, most practicing clinicians have little or no direct experience diagnosing or managing the disease. Over the past two weeks, DOH measles experts conducted both in-person and virtual medical briefings reaching more than 1,000 doctors, nurses, and other health care providers. The briefings covered recognition of signs and symptoms and reinforced the importance of encouraging patients to remain current on vaccinations. DOH has also issued multiple Health Alert Network messages to clinicians statewide.
“High rates of vaccination in a community reduce the spread of the highly contagious measles virus,” said Secretary of Health Dr. Debra Bogen. “The Department of Health is working hand in hand with a host of community partners to ensure people across the state have access to accurate information and to vaccines close to home.”
School Vaccination Data to Become Publicly Available
One notable policy development in the response is DOH’s announcement that school-level vaccination data will be published online within the coming weeks. Currently, vaccination coverage data is available only at the county and state levels. Making school-level data publicly accessible will give families more granular information to inform personal health and education decisions — and may help identify specific institutions or communities where coverage gaps increase outbreak risk.
Sources and further reading:
Shapiro Administration Taking Action to Contain Spread of Measles – Department of Health, Commonwealth of Pennsylvania