Top World Health Organization (WHO) officials are concerned that the United States President Donald Trump’s move to alter his country’s childhood vaccinations via an executive order will endanger children.

“WHO is concerned that the changes to immunisation policy in the US are not aligned with the best science,” Director-General Dr Tedros Adhanom Ghebreyesus told a media briefing on Wednesday.

The order recommends fewer vaccinations, separate vaccinations per clinic visit and – most controversially – that the combined measles, mumps, rubella (MMR) vaccine be “administered in three separate single-disease shots”,

“Delaying vaccines or separating doses unnecessarily does not make vaccination safer and can leave children unprotected,” said Tedros.

Every parent wants to keep their children safe, and vaccines are among the most powerful tools for doing that, making deadly diseases preventable. @WHO is concerned that recent changes to US immunization policy are not aligned with decades of evidence that show when children… pic.twitter.com/vCfgJFrFGK

— Tedros Adhanom Ghebreyesus (@DrTedros) August 12, 2026

WHO Assistant Director-General Dr Jeremy Farrar pointed out that the measles vaccine alone had saved 59 million lives.

“In many countries, including the United States, there are extensive measles outbreaks, which are causing huge concern,” said Farrar.

Measles, mumps and rubella are not mild diseases, Farrar said, adding that they can have severe complications: “If anybody has seen a child with post-measles encephalitis, you will remember it for the rest of your life.” 

Encephalitis is the inflammation of the brain and can cause brain damage.

Measles is one of the most infectious diseases, transmitted via infected droplets in the air. Unvaccinated individuals or those with unknown vaccination status represent almost all reported measles cases in the US.

Making it harder for parents

Dr Kate O’Brien, WHO’s director of Immunisation, Vaccines and Biologicals, warned that Trump’s decree is “going in exactly the wrong direction, and there is no evidence that would drive this decision”.

“Anything that is done that makes it harder for a parent to get the vaccines their kids need to protect them from what are serious diseases – anything that’s done to make that harder – is not in service of the child,” said O’Brien.

“From decades of experience, we know that the more you can enable families to be able to do what they want to do, the higher the coverage and the protection of children is.”

Dr Birgitte Giersing, WHO unit head of vaccine research, development and policy, said that 179 of the world’s 194 countries use the MMR vaccination.

“Our concern about the breakup of combination vaccines is that these would then actually be far more difficult to deliver. 

“At the moment, the MMR schedule is a two-dose schedule with those three vaccines,” she said.  Breaking it up into three separate vaccinations would potentially mean children need six vaccinations instead of two.

Safe and effective

“We have extensive scientific evidence that combination vaccines are safe and effective. They enable us to reach [large] populations because there are multiple vaccines within a single shot. They are more acceptable generally to communities, and they really simplify the delivery of vaccines,” said Giersing.

“We are very concerned,” concluded Farrar. “WHO provides the global evidence for these vaccines through the Strategic Advisory Group of Experts on Immunisation.

“Individual countries, of course, make their own decisions about which policies to implement. But we call on all countries to use the evidence base, use WHO’s advice and guidance, and make the best policy decisions based on the scientific evidence, not on political interference.”

Image Credits: Johns Hopkins University.