More than half the world will be at a “high or very high risk” of measles outbreaks by the end of 2024, according to the World Health Organization (WHO).

Earlier this week, the global group warned that the viral infection — which is also known as rubeola — has been increasing across the globe due to a high amount of vaccinations missed amid the COVID-19 pandemic.

“What we are worried about is this year, 2024, we’ve got these big gaps in our immunization programs, and if we don’t fill them really quickly with the vaccine, measles will just jump into that gap,” Natasha Crowcroft, a Senior Technical Adviser on Measles and Rubella with the WHO, said during a press briefing in Geneva.

“We can see, from data that’s produced with WHO data by the CDC, that more than half of all the countries in the world are going to be at high or very high risk of outbreaks by the end of this year,” she added.