US measles outbreak: cases pass 5,000, the highest in 35 years, as vaccination rates fall

The United States has recorded 5,182 confirmed measles cases so far this year, the highest number since 1991, according to the Centers for Disease Control and Prevention (CDC).

That is more than double the 2,289 cases recorded in 2025. Almost all the cases are linked to outbreaks, and nearly six in ten are among children and teenagers under 20.

Pennsylvania is the hardest-hit state, with 1,487 cases and six deaths this year. The CDC's national count lists four deaths, after it removed two Pennsylvania deaths from its tally when Health Secretary Robert F. Kennedy Jr. questioned whether measles caused them.

The US declared measles eliminated more than 20 years ago. Experts blame the return of the disease on falling vaccination rates: the share of kindergarten children who are vaccinated has dropped from 95.2 per cent in 2019-20 to 92.4 per cent.

Measles is highly contagious and can cause pneumonia, brain swelling and death, especially in young children. Two doses of the MMR vaccine give about 97 per cent protection. In Nigeria, measles vaccines are free at primary health centres.