US 2025 pertussis and measles outbreaks show most cases among vaccinated

In 2025, public‑health data from the United States revealed that a large proportion of pertussis and measles cases occurred in people who were up to date with their vaccinations. In West Virginia, health officials reported that 71 % of pertussis cases that year were among individuals fully vaccinated, and a review of the previous seven years showed 68 % of all pertussis cases involved vaccinated persons.

In New York, the 2025 measles outbreak comprised 18 confirmed cases. Of these, 33 % had received at least one dose of the MMR vaccine, seven had received none, two had one dose, four had two doses, and five cases had an unknown vaccination status. Legal advocacy group ICAN used the findings to question current vaccination policies, sending a letter to the Centers for Disease Control and Prevention urging that routine vaccines be re‑classified under a shared‑clinical‑decision framework.

The reports challenge assumptions about herd immunity and have been cited by authorities as justification for stricter vaccine mandates and the denial of medical exemptions.