The number of measles cases around the world rose by 20% in 2023 compared with 2022, leading to an estimated 10.3 million cases, according to estimates released Thursday by the World Health Organization and the U.S. Centers for Disease Control and Prevention.

The surge in the preventable disease was driven by “inadequate immunization coverage,” the agencies said in a joint statement.

More than 22 million children did not receive a first dose of the two-dose measles vaccine in 2023, the WHO and CDC said. Globally approximately 83% of children received a first dose of the vaccine last year, and 74% received a second dose, the agencies said.

Health officials recommend vaccination coverage of at least 95% in communities to prevent outbreaks. An infected person can spread the highly contagious disease to up to 90% of people close to them if they are not immune, according to the CDC.

“The number of measles infections are rising around the globe, endangering lives and health,” CDC Director Mandy Cohen said in the statement. “The measles vaccine is our best protection against the virus, and we must continue to invest in efforts to increase access.”

An estimated 107,500 people, who were mostly children younger than 5 years old, died from measles in 2023, the agencies said, adding that while that total represented was an 8% decrease from the year before, “far too many children are still dying from this preventable disease.” The agencies said the “slight reduction in deaths” was mainly because the surges took place in countries and regions of the world where children with the disease were less likely to die, due to their ability to access nutrition and health services. 

Measles symptoms commonly include a high fever, cough, conjunctivitis (pink eye), runny nose, white spots in the mouth and a rash that spreads from head to toe. Infants and young children are most at risk of serious complications from the disease such as pneumonia or swelling of the brain.

Vaccination coverage for measles fell globally during the pandemic to the lowest levels since 2008.

The WHO and CDC said that because of worldwide gaps in vaccination, nearly 60 countries in 2023 “experienced large or disruptive measles outbreaks in 2023, affecting all regions except the Americas,” an almost 60% increase from 36 countries in 2022. 

“Measles vaccine has saved more lives than any other vaccine in the past 50 years,” WHO Director-General Dr. Tedros Adhanom Ghebreyesus said in a statement. “To save even more lives and stop this deadly virus from harming the most vulnerable, we must invest in immunization for every person, no matter where they live.”