Chester County Health Department Director Jeanne Franklin warned that measles transmission from neighboring Lancaster County is likely, as the statewide outbreak nears 1,000 confirmed cases.

"We have a very long border with Lancaster county, and these types of disease don't care about borders," Franklin said, according to MyChesCo.

Chester County had 83 confirmed measles cases as of Oct. 2, the third-highest total of any county in Pennsylvania. Only Lancaster County, with 363 cases, and Mifflin County, with 106, had more, Patch reported. Chester County added 18 new cases in the two weeks before Oct. 2.

Statewide, Pennsylvania recorded 977 confirmed cases across 39 counties as of Oct. 2, according to the state Department of Health. The outbreak has caused 195 hospitalizations since it began in late April. Five people have died. Nearly 20% of people diagnosed with measles during the outbreak have been hospitalized.

Only four of the 977 confirmed cases involved vaccinated people, accounting for less than 1% of infections.

West Chester schools fall below vaccination threshold

Chester County's kindergarten measles vaccination rate falls just below the 95% threshold scientists say is needed to prevent wide spread, the Philadelphia Inquirer reported. Five elementary schools in West Chester had kindergarten vaccination rates below that mark.

The Chester County Health Department has given more than 500 MMR vaccine doses in 2026, most since the outbreak began. Department nurses will also bring doses to homes and farms of residents who do not travel, the Inquirer reported.

Dale Weiser, clinical services supervisor for the Chester County Health Department, said the department is racing to vaccinate residents before the virus reaches unprotected pockets of the population, according to the Inquirer.

Franklin told 6abc on Sept. 16, when Chester County had 65 confirmed cases, that outreach workers tailor their approach to each community's level of awareness, starting with basic education about measles before discussing the vaccine.

Statewide vaccination surge

The outbreak has driven a sharp increase in MMR vaccinations across Pennsylvania. The state typically records about 25,000 MMR doses per month. That number jumped to more than 49,000 in August and topped 53,000 in September. State health center staff have administered more than 5,600 MMR vaccinations through 189 pop-up clinics in affected communities since late April.

Two doses of the MMR vaccine provide about 97% protection against measles, according to the Pennsylvania Department of Health. People with two documented doses do not need another shot.

How to get help

The virus is highly contagious. It spreads through the air when an infected person breathes, coughs or sneezes and can remain infectious for up to two hours after that person leaves an area.

Symptoms typically begin with fever, cough, runny nose and red, watery eyes, followed days later by a rash that starts on the head and spreads downward. Symptoms can appear seven to 21 days after exposure.

Residents who believe they were exposed and develop symptoms should contact a health care provider or call the Pennsylvania Department of Health at 877-724-3258. The Chester County Health Department offers MMR vaccinations by appointment at 610-344-4414. More information is available at the county's measles page.