Pennsylvania has logged 1,000 measles cases, among the biggest outbreaks in decades

Key Points:

• Pennsylvania has surpassed 1,000 measles cases in 2026, marking one of the largest U.S. outbreaks in decades, with 992 cases linked to an outbreak that began in April and five measles-related deaths reported.
• The outbreak is concentrated in counties with low vaccination rates, particularly Lancaster and Chester counties, where Amish, Mennonite, and other communities have historically limited vaccine use, contributing to rapid virus spread across 39 of 67 counties.
• Approximately two-thirds of cases have involved adults, with a hospitalization rate of about 20%, higher than the national average, possibly due to underreporting of mild cases among children and reluctance to cooperate with health authorities.
• Despite an overall state vaccination rate near 94.5%, Pennsylvania’s permissive exemption policies and vaccine hesitancy have undermined herd immunity, allowing the highly contagious measles virus to spread widely.
• Public health officials face challenges in outbreak containment due to community resistance to quarantine measures, difficulties in contact tracing, and widespread misinformation fueling vaccine refusal.