RFK Jr.'s vaccine advisers stop recommending MMRV vaccine for kids under 4, delay vote on hepatitis B shot

A panel of experts at the U.S. Centers for Disease Control and Prevention has voted to change its recommendations on how children under four years of age should be vaccinated against measles, mumps, rubella and varicella (MMRV), while a planned vote on the Hepatitis B vaccine for young children will be delayed.

The Advisory Committee on Immunization Practices voted 8 to 3 (with one abstaining) on Thursday to recommend against allowing parents to choose a combined MMRV vaccine for children under the age of four. Instead, they recommend the use of a combined measles-mumps-rubella shot and a separate one for varicella (also known as chickenpox).

The panel of experts is in the midst of two days of meetings where they are reviewing vaccine recommendations. They were expected to vote on delaying the first hepatitis B shot until at least one month of age in infants born to mothers who test negative for the virus. That vote was postponed until Friday morning and then pushed off again.

The group did, however, vote in favour of testing all pregnant women for hepatitis B. A vote on COVID-19 vaccine recommendations is still expected to come later today.

The panel was hand-selected by Health and Human Services Secretary Robert F. Kennedy Jr., who ousted all of the advisory panel's previous 17 members.

He appointed eight new experts to the panel days later, and then added another five this week — many of whom have been skeptical of vaccine safety and accused of spreading misinformation.

The group's job is to advise the CDC on U.S. vaccination schedules. As the top health body in the country, doctors look to the CDC on how to advise their own patients, and many insurers make decisions about what vaccines they'll pay for based on CDC recommendations.

WATCH | RFK Jr. vs. U.S. Senate: The 3-hour vaccine showdown:

In an intense three-hour showdown, U.S. senators grilled Health Secretary Robert F. Kennedy Jr. on vaccine policy and his firing of the head of the Centers for Disease Control. Andrew Chang breaks down key moments in the heated exchanges between Kennedy and both Democrats and Republicans, and why he is facing increased scrutiny now in particular.

The combined MMRV shot was previously an option for children 12 months of age or older, though the CDC already recommends that separate MMR and varicella vaccines be given under age 4 unless parents express a preference for the combined shot.

The panel made their decision based on the risk of febrile seizures (a convulsion caused by a fever), which occasionally occur in kids after they've been given the first dose of the combined vaccine, though it is rare.

According to the CDC's own data, these seizures only occur in eight kids per 10,000 who get the combined MMRV shot. There's also a very small risk of febrile seizures with the split MMR and chickenpox vaccines — about 4 in 10,000.

These seizures can also occur when children have a fever due to an illness — including from infection with diseases like chickenpox or measles — and also don't usually cause long-term harm.

In the wake of the vote, the American Academy of Pediatrics (AAP) said the CDC's meeting promoted "misguided information" about childhood vaccines.

"Following today's meeting, instead of emerging with clear guidance about vaccines that we know protect against serious illnesses, families are left with confusion, chaos and false information," the association's president said in a statement.

The AAP added that the organization still sees both the MMRV and hepatitis B vaccine as safe and has made no changes to their recommendations for those shots.

While the CDC is still recommending that people get vaccinated against all four of the infectious diseases, University of Saskatchewan virologist Angela Rasmussen says the decision will require parents to book additional vaccine appointments and have their kids sit through more shots. That added layer of difficulty might mean some kids simply don't get vaccinated against the full slate of illnesses, she said.

She says vaccine uptake in the U.S. has already been declining, and that an added layer of difficulty will mean more kids will go unvaccinated and end up getting sick.

"Adding another mechanism … for reducing vaccine uptake is going to have huge consequences in terms of measles epidemics that have happened recently, and in fact are ongoing," Rasmussen said.

None of the CDC votes directly affects Canadians or the recommended use of either of those vaccines north of the border.

In Canada, the National Advisory Committee on Immunization (NACI) recommends either the combined MMRV vaccine or the MMR shot and separate varicella vaccination at 12 to 15 months of age, and a second dose at 18 months or sometime before the child starts school.

But aside from the CDC's role in the U.S., they've also historically played a leading role in vaccine research and policy that other countries have followed. Rasmussen says that a lack of access to quality data and expertise south of the border will hurt Canada's ability to make good policies, even if Canada leaves its guidelines as is.

Canada also buys a lot of vaccines from the U.S., according to Dr. Donald Vinh, an infectious disease specialist at the McGill University Health Center. If changes to the CDC's recommendations lead to less demand for the MMRV shot, it could mean less production from U.S. makers — which could affect Canadian supply.

"We're not talking about just the medical decision, but also the logistics," Vinh said.

Plus, viruses and vaccine misinformation alike can't be contained by borders, Rasmussen says. She points out that due to skepticism about the MMR and MMRV vaccines, rates of vaccination against those diseases have been dropping within Canada already.

"If people begin importing these preventable diseases [when travelling], and the vaccination rates get low enough in Canada, we'll start seeing outbreaks of those pathogens as well," Rasmussen explained. "Where the U.S. goes, many other countries follow."

Under Kennedy's leadership, the committee has undergone a dramatic transformation in recent months.

In early June, Kennedy ousted all of the advisory panel's 17 members. He appointed eight new experts to the panel days later, and then added another five this week. While some of them had served on CDC or FDA committees before, many have previously been skeptical of infectious disease spread, vaccines, or both.

One of the appointees, Retsef Levi, has previously cast doubt on the safety of mRNA vaccines, saying they can cause serious harm and death, especially among children, according to Reuters.

Martin Kulldorff, another of RFK's picks and chair of the committee, was also an architect of the Great Barrington Declaration — a document published in October 2020 that advocated against COVID-19 lockdowns. He co-founded a journal that has raised speculation among scientists and health experts who worry it might become home to dubious information, and was also fired from Harvard University in 2024 when he refused to get vaccinated.

On Thursday, Kulldorff defended the credibility of those on the panel and called himself the most "pro-vaccine scientist in the country." He also said his opponents should be willing to test their science in a debate — which he said he'd be willing to have publicly with past CDC directors.

"The members of this … committee are committed to reassuring the public and restoring public confidence [in vaccines] by removing unnecessary risk and harms whenever possible. That is a pro-vaccine agenda," he said.

"False accusations that we … are unscientific and dangerous antivaxxers, that just adds legitimacy to anti-vax positions, damaging both public health and the confidence in vaccines."