The number of measles infections in the commonwealth reached 943 cases across 39 counties as of Wednesday, state data shows. About one in five people have been hospitalized.
Nearly all cases involve unvaccinated people, according to health officials. That group can include infants who are not yet eligible for the measles, mumps and rubella vaccine, which is 97% effective in preventing a viral infection.
There have been four recorded measles cases in vaccinated people, representing less than 1% of all infections statewide. State health leaders have said the number is in line with the vaccine’s efficacy rate.
The Pennsylvania Department of Health reported the state’s first two measles-associated deaths in August. Both victims were infants in Lancaster County. State leaders reported two more deaths earlier this month — an 18-year-old from Mifflin County and a 40-year-old woman in Jefferson County.