Declining vaccination rates in Allegheny County—1 in 3 kindergarten classrooms lack herd immunity for measles

As the risk of measles remains an ongoing concern, herd immunity in Allegheny County, Pennsylvania, is already slipping. According to data obtained via The Washington Post in January 2026, 1 in 3 Allegheny County kindergartners were in a classroom too far below adequate vaccination coverage to stop a measles outbreak during the 2023–24 school year.