This was one in a continuing line of moves that have put Kennedy's vaccine skepticism into public policy, though scientists say the vaccines are safe.

The US Department of Health and Human Services (HHS) plans to cancel $500m (£376m) in funding for mRNA vaccines being developed to counter viruses that cause diseases such as the flu and Covid-19.

Moderna Inc. shares are selling off Wednesday, after the Trump administration took aim at the science behind the biotechnology company’s vaccines and said it would cancel some contracts and stop funding mRNA drug development.