Pennsylvania health officials reported 55 additional measles cases on Friday, as the state continues working to control an outbreak that has now reached dozens of counties.
The Pennsylvania Department of Health said 890 cases had been confirmed in 39 counties so far this year. The outbreak has led to 173 hospitalizations and four measles-related deaths, according to the agency.
Fewer than 1% of the reported infections occurred in people who had been vaccinated against measles, state officials said. Residents under 18 account for 31% of the cases.
The health department said it is working proactively with residents, community groups and medical providers to curb the outbreak by expanding access to reliable information and measles, mumps and rubella, or MMR, vaccinations.
Pennsylvania’s latest update came after Robert F Kennedy Jr, the Trump administration’s health secretary and a longtime vaccine skeptic, questioned the state’s measles-related fatalities. In a social media post, he said the deaths “may even have been altogether fabricated” for political purposes.
In August, the newly appointed director of the US Centers for Disease Control and Prevention instructed agency employees to leave two Pennsylvania measles-associated deaths out of the national count while officials reviewed what the CDC described as “additional information”.
Lancaster county has been Pennsylvania’s hardest-hit area this year, with 359 confirmed infections recorded in state data.
Since the outbreak began in late April, officials said, more than 5,300 MMR doses have been administered through 165 pop-up vaccination clinics in affected communities.
Health officials said dozens more clinics are planned over the coming weeks and months, depending on demand and local needs.
Across Pennsylvania, staff at state health centers have given residents more than 7,900 MMR vaccine doses this year. Medical providers statewide have also reported a sharp increase in interest from people seeking vaccination, the department said.
The Department of Health said full vaccination remains the strongest defense against measles. The agency states that the MMR vaccine strengthens the immune response and delivers 97% lifetime protection.
Measles is highly contagious and can lead to serious complications. Although deaths are uncommon, the health department said the disease is fatal in one to three patients for every 1,000 cases.
The United States declared measles eliminated in 2000, but the virus has returned in communities where vaccination rates are low.
The CDC says measles spreads through coughing and sneezing. The virus can also remain suspended in the air for as long as two hours after an infected person has left a space.
Symptoms typically appear seven to 14 days after exposure. They may include a high fever, cough, runny nose and red, watery eyes, followed by a rash that moves down the body.
According to the CDC, receiving both recommended doses of the MMR vaccine offers the best protection against measles.
CDC data showed that more than 3,659 measles cases had been confirmed across the US as of 24 September. Nationwide, 2,289 confirmed cases were reported during the whole of 2025.
