Pennsylvania health officials have now detected measles cases in York and Northumberland Counties as cases in Lancaster County, the center of an ongoing outbreak, continued to rise.
And the state health department is now recommending early measles vaccinations for infants beginning at 6 months in affected areas in an effort to protect them against the spread of the highly contagious disease, which is particularly risky for young children. The same precautions should be taken by families with infants traveling to these areas.
Six Pennsylvania counties have now seen measles cases since an outbreak was first confirmed in Lebanon County in April. In all, the state has reported 81 measles cases across eight counties in 2026, more than five times the cases reported in 2025.
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State health officials said it was too early to tell how the latest cases in York and Northumberland Counties are connected to others in the region, but that contact tracing investigations are continuing. All cases were among people who had not received at least two doses of the measles, mumps, and rubella (MMR) or whose vaccination status was unclear.
As of Wednesday, six cases had been confirmed in Northumberland County, to the north of Dauphin County, and one case had been detected in York County, along Lancaster’s western border.
Lebanon County has reported 20 cases and Dauphin and Berks Counties have reported two cases each.
Lancaster County has seen 38 cases of measles since late April, with health officials confirming seven cases in the last two weeks. The area was at the center of a prior measles outbreak in January, when state health officials confirmed eight cases in Lancaster County and an additional four between Chester and Montgomery Counties.
Vaccination rates among kindergarteners have decreased across Pennsylvania in recent years, and some counties affected in the current outbreak have particularly low rates, including Lancaster, where about 88.5% of kindergarten students are vaccinated. Health experts say that 95% of a community must be vaccinated to prevent the spread of the disease.
Health officials have been conducting contact tracing to detect as many cases as possible. In the current outbreak, they have twice warned Lancaster residents that they could have been exposed to measles.
Shoppers and employees at a local Kohl’s were potentially exposed to the virus over four days after a staffer tested positive in late May, LancasterOnline reported. And a person with measles visited the Lancaster County Courthouse on June 3.
But doctors in Lancaster County say they fear some measles cases are going unreported, either because patients don’t understand the importance of tracking measles cases or because they fear repercussions.
No cases have been confirmed in the Philadelphia region during this outbreak. But Delaware County health officials said last week that they had detected measles in two wastewater samples, indicating that someone with measles had used a bathroom connected to the county’s public water supply. It was unclear if that person lived in the county or was passing through.
Early vaccination recommended
On Wednesday, a statewide health alert urged physicians to accelerate vaccination schedules to protect children against measles. Officials had said they were considering the measure earlier this month as cases continued to rise.
Measles can infect nine in 10 unvaccinated people who are exposed to it, and can linger in the air for up to two hours and incubate in patients for three weeks. The disease typically presents with a fever and a rash but can cause brain inflammation and pneumonia in serious cases.
Typically, children receive the first of two MMR vaccines at 1 year old, then a second between 4 and 6 years old.
But children as young as 6 months can receive an additional “dose zero” to protect them from the disease amid an outbreak. In its alert, the state health department said parents should vaccinate infants between 6 and 11 months with the “dose zero” if they live in affected areas or if they’re planning to travel there.
Those children should then receive additional MMR doses at 12 to 15 months and 4 to 6 years.
This “dose zero” is less effective than doses given at 1 year old, officials cautioned. But it’s 58% effective against measles when given at 6 to 8 months, and 83% effective when administered at 9 to 11 months.
“Early MMR vaccination is safe and provides modest protection when measles is spreading,” officials wrote in the alert.
Children older than 12 months who haven’t been vaccinated should get an MMR dose immediately, and a second 28 days later, health officials said. Unvaccinated adults, or those without evidence of immunity, should also get two MMR doses.
And anyone who has received one dose of the MMR vaccine in the past should get a second at least 28 days after their first, officials said.
Usually, children who received a first dose at around 12 months wait to get their second dose until they’re 4 to 6 years old. But in an outbreak situation, those children should get their second doses early — at least 28 days after their first shot.
Adults born before 1957 are typically considered immune, but healthcare workers in that age group who don’t have lab evidence of immunity or prior infection should consider getting vaccinated, state officials said.
Adults who received an inactivated measles vaccine between 1963 and 1967 are considered unvaccinated during an outbreak, and should also get two doses of the current MMR vaccine.
Pregnant people, people with severely weakened immune systems, and people who have a history of experiencing severe allergic reactions, like anaphylaxis, to a vaccine ingredient or to a previous dose of MMR cannot receive the vaccine.
