169 million children worldwide have missed out on the measles vaccine in the last eight years.
The charity Unicef said increasing numbers of youngsters are being left unprotected against measles, which can cause disability and death.
Inaccurate and misleading anti-vaccination messages on social media are thought to be one reason why vaccination rates are plummeting.
Unicef's analysis shows that an estimated 169 million children around the world missed out on the first dose of the measles vaccine between 2010 and 2017 - an average of 21.1 million a year.
A list of 10 high-income countries, published by Unicef, shows the US has the highest number of children missing out on their first dose of the vaccine.
Between 2010 and 2017, some 2,593,000 youngsters in the US did not have their first dose of the vaccine.
The second most affected country was France, with 608,000 unvaccinated children over the same time period, followed by the UK, with 527,000.
Other countries including Argentina, Italy, Japan, Canada, Germany and Australia also made the top 10.
Unicef executive director Henrietta Fore said: "The measles virus will always find unvaccinated children.
In the first three months of 2019, more than 110,000 measles cases were reported worldwide - up almost 300% on the same period the year before.
An estimated 110,000 people, most of them children, died from measles in 2017, a 22% rise on the previous year.
Children need two doses of the vaccine for protection, with the World Health Organisation (WHO) recommending 95% coverage to achieve herd immunity, which offers protection against the disease spreading in the community.
Executive Director of UNICEF Ireland, Peter Power, said it is a worry even in developed countries, including Ireland.
He said: "In Ireland, for example, the cases of measles have doubled in the last three years.
"Children can die if they contract measles. The vaccine is very effective and we encourage all parents to have their children vaccinated."
Globally, 85% of children received their first dose in 2017 and 67% got the second dose.
Unicef said the rates reflected "lack of access, poor health systems, complacency, and in some cases fear or scepticism about vaccines".
PA & Digital Desk