Global measles cases and deaths are on the rise, as too many children are not being vaccinated, health officials said Thursday.

According to a report by the U.S. Centers for Disease Control and Prevention and the World Health Organization, the number of measles cases increased by 18% from 2021 to 2022, up to 9 million, while deaths spiked by 43%, to 136,000.

Children accounted for most of the deaths, the report said.

“The increase in measles outbreaks and deaths is staggering, but unfortunately, not unexpected given the declining vaccination rates we’ve seen in the past few years,” John Vertefeuille, director of the CDC’s global immunization division, said in a statement. “Measles cases anywhere pose a risk to all countries and communities where people are under-vaccinated. Urgent, targeted efforts are critical to prevent measles disease and deaths.”   

In 2022, 37 countries experienced large or disruptive measles outbreaks, compared to 22 countries the year before, according to the study. Of the 37 countries with outbreaks, 28 were in Africa, six were in the eastern Mediterranean, two were in southeast Asia and one in Europe.

Measles is preventable with two doses of a vaccine. There was a modest increase worldwide in inoculations from 2021 to 2022, but 33 million children still missed a vaccine dose, the report said.

Health experts say a 95% vaccination rate is needed to protect communities from outbreaks. The global rate is 83% for a first dose and 74% for a second, according to the analysis.

Low-income countries have the lowest vaccination rates, at 66%, the report said. That number declined during the COVID-19 pandemic and has not rebounded.

According to the analysis, of the 22 million children who did not receive their first vaccine dose, more than half live in just 10 countries: Angola, Brazil, Democratic Republic of the Congo, Ethiopia, India, Indonesia, Madagascar, Nigeria, Pakistan and the Philippines. 

“The lack of recovery in measles vaccine coverage in low-income countries following the pandemic is an alarm bell for action,” Kate O’Brien, WHO’s director for immunization, vaccine and biologicals, said in a statement. “Children everywhere have the right to be protected by the lifesaving measles vaccine, no matter where they live.”

The CDC and WHO are urging countries to find and vaccinate all children against measles and other vaccine-preventable diseases. They also are calling for health organizations at the global, regional, national and local levels to invest in robust surveillance systems and outbreak response capacity. 

The report did not address measles cases in the United States specifically, but it noted that the Americas and Europe were the only regions that saw a decline in measles vaccination coverage from 2021 to 2022, dipping from 85% to 84% in the Americas.

A separate CDC study earlier this year found that vaccination rates for kindergartners for measles, mumps, polio, chickenpox and other diseases fell from 95% in the 2019-20 school year to 93% in 2021-22. The difference translated into at least 250,000 children not being protected, officials said. 

Health experts blamed the COVID-19 pandemic for the lower vaccination rates. They said the pandemic resulted in fewer parents taking their children to doctors for checkups, schools relaxing immunization policies and misinformation about COVID-19 shots possibly hurting confidence in other vaccines.

But measles cases in the U.S. are still far less frequent than they once were. According to the new report by the CDC and WHO, there were an estimated 8,770 cases and three deaths in the U.S. in 2000, but only 825 cases and one death in 2022.

According to CDC data, there were nearly 2½ times more U.S. measles case in 2022 than 2021, increasing from 49 to 121. But there have been just 41 reported cases this year, as of Nov. 2.