Stocks in drug makers slumped after Donald Trump named vaccine sceptic Robert F Kennedy Jr as his health secretary.

Shares in London-listed pharmaceuticals giant GSK, which makes vaccines for measles and mumps, dived by as much as 4pc on Friday morning, dropping to their lowest levels in two years. AstraZeneca, which developed a vaccine for the Covid-19 virus, dropped by 3pc.

Paris-listed Sanofi, which makes flu vaccines, was down as much as 4.4pc to hit a four-month low.

In the US, Covid-19 vaccine maker Moderna was down by more than 2pc in pre-market trading, while BioNtech was down 2pc.

The declines came after Mr Trump said he would make Mr Kennedy Jr, who is the nephew of John F Kennedy , his health secretary to “make America great and healthy again”.

Mr Kennedy Jr – known as RFK Jr – has previously voiced anti-vax opinions and suggested fluoride is lowering children’s IQ. He once said: “There’s no vaccine that is safe and effective”.

Analysts at JP Morgan said: “Admittedly, it is difficult to evaluate the exact impact this appointment could have on the industry until we have more information on specific policy proposals and priorities of the incoming administration on healthcare and the drug industry.

“That said, we are not surprised the sector has been under pressure on the potential for RFK Jr. having oversight of the various agencies within HHS [Health and Human Services] (including the FDA, the CDC, NIH, and Medicare/Medicaid) given his previous stated views on the industry.”

Mr Kennedy Jr urged people to “resist” guidelines on when children should be vaccinated during the pandemic and has been accused of spreading misinformation regarding vaccines, including promoting debunked theories linking childhood vaccines to autism.

Dr David Elliman, a consultant at Great Ormond Street Hospital, said: “What is really concerning are his views on vaccination. He has perpetuated myths, including that of a link between MMR vaccine and autism, with an utter disregard for the evidence.

“If he is appointed and continues in the same mode, I fear not just for the vaccination programme in USA, but similar programmes around the world, and for healthcare, in general.”

While he is sceptical of vaccines, Mr Kennedy Jr has said that “we’re not going to take vaccines away from anybody”.

Healthcare experts expressed alarm at Mr Kennedy Jr’s appointment. Public Citizen, a US-based nonprofit consumer advocacy organisation, called RFK Jr a “clear and present danger to the nation’s health”.

Robert Weissman, co-president of Public Citizen, said: “By appointing Kennedy as his Secretary of HHS, Trump is courting another, policy-driven public health catastrophe.”