Robert F Kennedy Junior’s hand-picked vaccine advisory panel has voted to revise the recommendation for major childhood vaccines.

In a decision on Thursday, the panel voted 8-3, with one abstention, that children aged four and under should no longer receive the combined measles-mumps-rubella-varicella (MMRV) vaccine.

Instead, it said that the children should be given the measles, mumps and rubella (MMR) and varicella, or chickenpox, shots separately.

The move does not amount to a withdrawal of approval for either vaccine, which are both still recommended to prevent the potentially fatal diseases.

This decision may lead parents to face difficulties in procuring the combined vaccine for young children, which has been associated with a slightly elevated risk of febrile seizures compared to giving the shots separately during the same doctor’s visit.

At present, the CDC advises that the first dose of MMR and varicella should be given separately unless a parent requests the combined version.

This vote was the first from Kennedy’s new 12-member Advisory Committee on Immunization Practices (ACIP), which includes several members who have expressed skepticism towards vaccine use.

Kennedy, a longtime vaccine sceptic, has said re-examining the childhood vaccine schedule is needed to restore confidence in public health agencies.

Shown above is the panel debating the CDC’s vaccine recommendations in Atlanta, Georgia

However, Merck, the manufacturer of the combined shot, criticized the decision, arguing it ‘occurred in the absence of new scientific data and contradicts years of evidence supporting the current immunization schedule’.

Experts also expressed concern, with Dr. Aaron Milstone, pediatric infection control chief at Johns Hopkins Children’s Center, cautioning that the change would ‘reduce access’ to protection against diseases that once affected tens of thousands of people annually. 

The recommendation still needs to be approved by the acting CDC director, Jim O’Neill, before it can become official guidance.

O’Neill took the place of Dr Susan Monarez who said she was fired for, in her words, ‘holding the line on scientific integrity’.

The vote came after a day-long meeting of the committee at the CDC’s headquarters in Atlanta, Georgia.

The committee is reconvening today, and is also expected to discuss guidance about the hepatitis B vaccine, which is administered in three doses at birth, one to two months and six to 18 months of age.  

The combined MMRV vaccine was first approved in the US in 2005. 

It combines the MMR shot, which is administered in two doses at 12 to 15 months and 4 to 6 years of age, and the chickenpox shot, which is also administered in two doses at the same ages.

But after data showed a higher risk of adverse reactions when using the combined shot as a first dose, the CDC advised against its use in children under four years, unless parents requested it.

Robert F Kennedy Junior has said revisions are needed to restore confidence in public health. He is pictured above yesterday in Washington, DC

The decision affects the vaccination schedule for children. The above is a stock image of a young child being vaccinated

The agency says that when first doses of the MMR and varicella shots are administered separately on the same doctors visit, about 15 out of every 100 children develop a fever and four out of every 10,000 suffer a febrile seizure.

But when the shots are given as a combined first dose, the risk of a fever rises to 22 out of every 100 children, while the risk of a febrile seizure doubles, to eight out of every 10,000 children.

Doctors say this may happen because the body triggers a broad, strong response to all four viruses being vaccinated against at the same time.

A febrile seizure can look dramatic, but it is typically lasts only a few minutes. A febrile seizure rarely results in long-term complications.

Doctors have not detected a higher risk of fever of febrile seizures when the MMRV vaccine is given as a second dose, which is likely because the immune system has been ‘primed’ by the first shot. 

Because the second dose is administered after age four, the new recommendation would not affect whether the MMRV can be used as a second dose. 

All the shots, both separate and combined, offer the same level of protection against the disease, that used to sicken tens of thousands every year before they could be vaccinated against.

Three to 4million people used to be infected with measles in the US every year, estimates suggest, while 48,000 were hospitalized and 400 to 500 people died from the disease.

While for chickenpox, estimates suggest the disease used to infect 4million children every year, and cause 10,500 to 13,500 hospitalizations and 100 to 150 deaths.

The US has had a measles elimination status since 2000, but has recorded 1,491 cases so far this year, the most since the disease was declared eliminated.

There are an estimated 100,000 to 150,000 cases of chickenpox recorded in the US every year.

If approved, the recommendation would have US guidelines on a par with countries like Australia and France, which say that the MMR and varicella vaccines should be given separately.

Other similar countries like Canada and Italy offer parents either the MMRV vaccine as a first dose for their children or the MMR and varicella shots as a first dose.

The UK has gone the other way, however, and is set to start offering the combined MMRV shot as a first dose from January 2026.