PENNSYLVANIA — The Centers for Disease Control and Prevention confirmed two measles-related deaths in the United States on Tuesday. The agency did not specify in which states the two measles deaths occurred.

This announcement comes as the US has recorded more measles cases this year than in any year since 1991. As of 24 September, the CDC confirmed a total of 3,659 measles cases in the US. The current outbreak affects 47 states.

Pennsylvania has reported at least 903 measles cases, including four measles-associated deaths. The CDC is not including Pennsylvania's four measles deaths in its national mortality data. The agency has shifted to using mortality data from the National Center for Health Statistics (NCHS) for its national measles death count. The CDC is relying on data from the NCHS to identify measles as the underlying cause of death until a standardized definition is created.

There is an ongoing dispute between Pennsylvania Governor Josh Shapiro and US Health Secretary Robert F Kennedy Jr regarding measles data discrepancies. Kennedy maintains that only one of the Pennsylvania deaths was caused by measles. The CDC is working with state epidemiologists to develop a standard definition of measles-related deaths. The agency is collaborating with the Council of State and Territorial Epidemiologists (CSTE) to develop a standardized case definition for these deaths.

Pennsylvania reported new measles cases in the seven days prior to the announcement. One third of these new cases were children under 18. The state has reported 176 measles hospitalizations.

Measles cases in Pennsylvania have been reported in 39 counties. Less than 1% of total measles cases in the state involve people who have been fully vaccinated. Only four fully vaccinated individuals in Pennsylvania have contracted measles.

The Pennsylvania health department said: "While daily numbers fluctuate, tracking these trends provides Pennsylvanians and health care providers with visibility into community transmission across the [state] and helps inform the department’s ongoing response." State health center staff in Pennsylvania have administered more than 7,900 MMR vaccine doses to residents in 2026. More than 49,000 MMR vaccines were administered in Pennsylvania in August 2026. More than 38,000 MMR vaccine doses were administered in the state during the first three weeks of September 2026. Pennsylvania reported new measles infections in the week leading up to September 28, 2026.

Measles was declared eliminated in the US in 2000. Deaths from measles occur in approximately one to three patients per 1,000 cases. Symptoms usually begin seven to 14 days after infection.

These symptoms can include high fever, cough, runny nose, red watery eyes, and a rash that spreads down the body. The CDC advises that two doses of the MMR vaccine provide the best protection against measles. The MMR vaccine is proven 97% effective at preventing measles for life after two doses.

Timeline

The Trump administration laid off 18% of CDC staff in 2025. In August, President Trump signed an executive order aimed at getting states to modify childhood vaccine recommendations by splitting the MMR vaccine into three separate shots and spacing out childhood appointments.

More than 38,000 MMR vaccine doses were administered in Pennsylvania during the first three weeks of September 2026.

What's New

Robert F Kennedy Jr maintains that only one of the Pennsylvania deaths was caused by measles. The CDC is relying on data from the National Center for Health Statistics (NCHS) to identify measles as the underlying cause of death, until a standardized definition is created.

The CDC is working with the Council of State and Territorial Epidemiologists to develop a standard case definition for measles-related deaths. The agency is collaborating with the Council of State and Territorial Epidemiologists (CSTE) to develop a standardized case definition for measles-related deaths.

Why It Matters

The discrepancy in mortality data shows the challenges in tracking disease outcomes during an outbreak. With the CDC excluding Pennsylvania's four deaths from its national count while the state includes them, the true toll of the epidemic remains a point of contention between federal and state officials. This dispute occurs as the nation experiences its highest case count since 1991, affecting 47 states.

The development of a standardized case definition for measles-related deaths by the CDC and the Council of State and Territorial Epidemiologists aims to resolve these inconsistencies. Until this definition is established, reliance on NCHS data means national figures may not reflect state-level reports. The situation shows the importance of consistent data collection methods for public health response and resource allocation.