A key US vaccine advisory committee has voted to stop recommending all adults get the Covid-19 vaccine, which has until now been officially approved for most Americans annually since the pandemic.

The Advisory Committee on Immunisation Practices (ACIP) also narrowly voted against advocating prescriptions for the Covid-19 vaccine.

In two days of meetings, Acip changed its recommendations on the combined measles, mumps, rubella, varicella (MMRV) vaccine, and delayed plans for a vote on the hepatitis B vaccine.

Health Secretary Robert F Kennedy Jr, a vaccine sceptic, fired all 17 members of the committee in June and handpicked their successors, sparking uproar in the medical community.

The panel spent Friday debating the Covid-19 vaccine, which has for the past several years been a routine recommendation, like the yearly flu jab.

Acip voted to abandon broad support for recommending the jab, including for high-risk populations like people aged over 65.

Instead it decided they could make their own decision after talking with a medical professional.

In May, the federal government stopped recommending Covid-19 vaccines for healthy pregnant women and children.

In one exchange on Friday, Kennedy's ally Dr Robert Malone argued there was no evidence that the Covid vaccine prevented serious infection.

Dr Cody Meissner, once part of the Food and Drug Administration's vaccines panel, argued there is "pretty well-defined" data that the jab protects against infection.

There was confusion during the debate over the MMRV vaccine - measles, mumps and rubella, and varicella (commonly known as chickenpox).

On Thursday, the panel voted against recommending the combined MMRV shot for children aged four and under.

But on Friday they decided to endorse two separate jabs - a combined one for measles, mumps and rubella, and another for varicella.

The American Medical Association, which represents doctors and medical students, said the new MMRV recommendations "leave parents confused".

The panel also delayed a vote on whether newborns whose mothers have tested negative for hepatitis B during pregnancy should automatically receive a jab for the liver virus.

The Acip has cast doubt on the hepatitis B vaccine for months, even though scientists say it is safe and effective at preventing the infection.

In June, the panel's new chairman Dr Martin Kulldorff questioned whether it was "wise" to give the hepatitis B vaccine to newborns.

The CDC has advised that children receive the hepatitis B vaccine at birth since 1991.

Since then, the number of cases of the potentially fatal disease have decreased among people aged 19 and younger, which experts and the CDC credit to the implementation of the hepatitis B vaccine.

Robert F Kennedy Jr's posture on vaccinations has been under scrutiny since he took office in January.

Kennedy has overhauled the CDC during his tenure. He replaced the members of the vaccine advisory panel in June, and fired its chief Susan Monarez in late August, provoking a group of senior staff to resign in protest.

On Wednesday, Dr Monarez told the Senate she was fired for refusing to sign off on changes to vaccine policy "regardless of the scientific evidence".

Earlier this month, Kennedy said he dismissed Dr Monarez because he felt their interactions demonstrated she was not trustworthy.

Doctors and health experts have criticised the health secretary's longstanding questioning of the safety and efficacy of several vaccines, although in his Senate confirmation hearing, he said he was "not going to take them away".