Infants around the world aren’t being properly immunized, according to the WHO.

According to a joint statement made yesterday by the Centers for Disease Control and Prevention and the World Health Organization, approximately 22 million infants in countries around the world missed their measles vaccines last year. By the WHO’s estimates, roughly two-third of these at-risk infants are based in Nigeria, India, the Democratic Republic of the Congo, Ethiopia, Indonesia, Pakistan, Angola, the Philippines, Brazil and Afghanistan. This is due to a combination of greater vaccine hesitancy, as well as more difficulty in getting access to vaccines in some parts of the world.

Measles is one of the most contagious viruses in the entire world, though according to the WHO, it is “almost entirely preventable” through the use of vaccines, which is why vaccination infants and children for measles has become a regular practice in recent decades. Unfortunately, anti-vaccination movements have led to infants missing their measles vaccines, which in turn leads to localized measles outbreaks. Only about 70% of infants worldwide have been fully vaccinated against measles, 25% below the recommended herd immunity threshold.

Dr. Kate O’Brien, the director of the WHO’s department of immunization, vaccines and biologicals, warned that “evidence suggests we are likely seeing the calm before the storm as the risk of outbreaks continues to grow around the world.”

“It’s critical that countries vaccinate as quickly as possible against COVID-19, but this requires new resources so that it does not come at the cost of essential immunization programs,” O’Brien said. “Routine immunization must be protected and strengthened; otherwise, we risk trading one deadly disease for another.”