Pennsylvania: The United States has recorded 5,182 confirmed measles cases so far in 2026, marking the highest annual total reported by the Centres for Disease Control and Prevention (CDC) since 1991, as outbreaks continue to spread with declining vaccination rates.
Measles, a highly contagious but vaccine-preventable disease, has affected children and teenagers disproportionately. According to CDC data, children under five account for 18 percent of confirmed cases, while those aged 5 to 19 represent 41 percent. Together, these age groups account for about 59 percent of all reported infections.
A total of 4,993 cases have been linked to outbreaks, highlighting the continued transmission of the virus across communities. The 2026 figure has already more than doubled the 2,289 confirmed cases recorded throughout 2025.
The rising number of infections comes with a decline in childhood vaccination coverage across the country. Measles vaccination coverage among US kindergarten students fell from 95.2 percent in the 2019–2020 school year to 92.4 percent in the 2025–2026 school year, increasing concerns about the risk of further outbreaks.
Dispute over measles-related deaths
The CDC has reported four measles-related deaths in 2026. However, this figure differs from state-level reports, particularly in Pennsylvania, which has been among the hardest-hit states. The Pennsylvania Department of Health has recorded six deaths and 1,487 confirmed cases this year.
The difference in reported fatalities has triggered a dispute between Pennsylvania Governor Josh Shapiro and US Health Secretary Robert F. Kennedy Jr. over how measles-related deaths should be classified and included in national statistics.
Pennsylvania classifies a death as measles-associated when a person with confirmed measles dies within 30 days of developing symptoms, unless the death is determined to have resulted from an unrelated cause. The CDC initially included two deaths of unvaccinated individuals reported by Pennsylvania in August but later removed them following questions over whether measles caused or contributed to the fatalities.
The CDC has stated that it is working with the US Council of State and Territorial Epidemiologists to establish a standardised definition for measles-related deaths. Public health experts have raised concerns that differences in reporting methods could affect the monitoring of the disease and its overall impact. Tracking measles-associated deaths has historically been part of the approach used by international health authorities, including the World Health Organisation (WHO).
Although the United States declared measles eliminated more than two decades ago, the latest surge highlights the continuing threat posed by declining immunisation rates. With infections also increasing in several parts of the world, experts warn that gaps in vaccination coverage can leave communities vulnerable to outbreaks, making sustained immunisation efforts essential to preventing further spread.
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