The World Health Organization says the spread of the coronavirus is disrupting routine vaccinations for nearly 80 million infants under the age of one.
WHO Director-General Tedros Adhanom Ghebreyesus told a news conference on Friday the pandemic has interrupted vaccination schedules in at least 68 countries.
He described any suspension of childhood vaccination services as a "major threat to life."
UNICEF Executive Director Henrietta Fore said vaccination campaigns to be especially badly hit include measles and polio.
Fore said health centers have been overwhelmed with response efforts to COVID-19. She added parents have been reluctant to take children to vaccination sites due to infection fears.
Also on Friday, WHO Executive Director for Emergency Programs Michael Ryan said South America has become the new epicenter for COVID-19. He said the continent is seeing increasing infections, with Brazil the most seriously affected.
Brazil has more than 310,000 confirmed cases. It ranks third-highest in the world for number of infections.