Worldwide measles vaccinations in children declined significantly during the COVID-19 pandemic, making the disease an “imminent threat” worldwide, according to a joint report released Wednesday from the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC).

In 2021, a record high of nearly 40 million children missed a measles vaccine dose: nearly 25 million children missed their first dose, an 11 percent increase from 2020. An additional 14.7 million children missed their second dose, the report found, the lowest levels of vaccination since 2008.

Delays increase the risk of measles outbreaks, and the agencies said now is the time for public health officials to accelerate vaccination efforts and strengthen surveillance.

“The record number of children under-immunized and susceptible to measles shows the profound damage immunization systems have sustained during the COVID-19 pandemic,” CDC Director Rochelle Walensky said in a statement. 

“Measles outbreaks illustrate weaknesses in immunization programs, but public health officials can use outbreak response to identify communities at risk, understand causes of undervaccination, and help deliver locally tailored solutions to ensure vaccinations are available to all,” Walensky said.

Measles is extremely contagious, but is almost entirely preventable through vaccination. A country needs at least a 95 percent vaccination rate in order to achieve herd immunity and eliminate the virus. 

But the world is well under that, as only 81 percent of children have received their first measles-containing vaccine dose, and only 71 percent of children have received their second vaccine dose.

Measles was declared eliminated in the U.S. in 2000, meaning the disease is no longer constantly present in this country. Outbreaks continue to occur among unvaccinated communities because of imported cases.

If an outbreak continues for a year or more, the United States could lose its measles elimination status, which nearly happened in 2019 due to outbreaks in the New York City area. That year, the U.S. saw more than 1,200 infections. To date in 2022, there have been 51 reported cases in the U.S. according to CDC.

Since 2016, 10 countries that had previously eliminated measles experienced outbreaks and reestablished transmission. 

“What’s concerning to us here at CDC is that the trends that continued at the beginning of the COVID-19 pandemic last year of declining vaccination coverage have continued for a second year,” said Cynthia Hatcher, one of the report’s authors who oversees CDC’s African measles elimination work.

“For a disease like measles that’s so highly infectious, that really leaves us with an enormous number of unvaccinated children and just very high levels of risk for outbreaks and for the disease to cross borders. … Measles anywhere is a threat everywhere,” Hatcher said in an interview. 

According to the report, there were an estimated 9 million cases and 128,000 deaths from measles worldwide in 2021. 

“The paradox of the pandemic is that while vaccines against COVID-19 were developed in record time and deployed in the largest vaccination campaign in history, routine immunization programs were badly disrupted, and millions of kids missed out on life-saving vaccinations against deadly diseases like measles,” WHO Director-General Tedros Adhanom Ghebreyesus said in a statement.

“Getting immunization programs back on track is absolutely critical. Behind every statistic in this report is a child at risk of a preventable disease,” Tedros said. 

Updated at 2:40 p.m.