There is now an "imminent threat" of measles spreading in every region of the world, the World Health Organisation and the US public health agency has said.
In a joint report, the health organisations said there had been a fall in vaccines against measles and less surveillance of the disease during the COVID pandemic.
Measles is one of the most contagious human viruses but is almost entirely preventable through vaccination, though it requires 95% vaccine coverage to prevent outbreaks.
A record high of nearly 40 million children missed a dose last year because of hurdles created by the pandemic, according to the report by the WHO and the US Centers for Disease Control and Prevention.
This has left millions of children susceptible to the disease.
"We are at a crossroads," Patrick O'Connor, the WHO's measles lead, said.
"It is going to be a very challenging 12-24 months trying to mitigate this."
Source: Sky News, 24 November 2022