An estimated 10.3 million cases of measles occurred worldwide last year, up 20% from 2022, primarily because of inadequate immunization coverage, according to the World Health Organization and the U.S. Centers for Disease Control and Prevention.

The disease resulted in 107,500 deaths last year, mostly killing children younger than 5, the two agencies said. Although that number was an 8% decrease from 2022, the reduction in fatalities was primarily because the increase in cases occurred in countries with better nutritional and health services, the WHO and CDC said.

But this concerning trend can be reversed with increased vaccination, they added. About 95% of the community or more must receive the full two doses of the measles vaccine to reduce the chance of outbreaks. Last year, 74% of children globally received two doses, while 83% received their first. More than 22 million children, however, were not vaccinated against measles.

“The number of measles infections are rising around the globe, endangering lives and health,” CDC Director Mandy Cohen said in a joint news release with the WHO.

“The measles vaccine is our best protection against the virus.”

Since 2000, immunization has prevented 60 million deaths worldwide, according to the WHO. Before the measles vaccine was rolled out in 1963, epidemics hit every two to three years, killing 2.6 million people each year. Wider vaccine coverage among infants reduces new measles cases for all ages, figures compiled by the data website Our World in Data show.

Measles is a highly contagious airborne disease, according to the WHO. It can cause high fever, coughs, runny noses and rashes, and result in serious health complications for children under 5, including ear infections, pneumonia and encephalitis, the CDC says.

U.S. vaccination numbers are down

American children have generally been well immunized against the disease, but coverage rates have declined in recent years. Kindergartners in the 2019-2020 school year had a 95.2% vaccination rate, while those in the 2023-2024 school year had a 92.7% rate. This means 280,000 kindergartners were vulnerable to measles, according to the CDC.

This year, 277 cases have been reported in the United States, with more than 114 - or 41% - involving children under 5. Close to 90% of those infected were not vaccinated, according to the CDC.

Even when children survive a measles infection, they may suffer from long-term effects, such as immune amnesia, or subacute sclerosing panencephalitis, a rare but fatal viral infection of the central nervous system.

Experience in Samoa

In 2019, a deadly outbreak hit Samoa, a Pacific island nation, killing at least 80 after infecting thousands in a country with nearly 220,000 people. Health officials have blamed inadequate vaccine coverage.

Robert F. Kennedy Jr. — the Health and Human Services secretary nominee widely known for his anti-vaccine views — at the time, questioned whether problems with the measles vaccine itself caused the Samoan outbreak, rather than insufficient vaccine coverage. Kennedy’s own family members have said he is spreading dangerous misinformation about vaccines.

The Children’s Health Defense, Kennedy’s advocacy group, did not immediately reply to a question about whether he still opposes measles vaccination.