Updated September 18, 2025 at 6:35 PM EDT
A panel of vaccine advisers to the federal government – now embroiled in controversy under the leadership of Health Secretary Robert F. Kennedy Jr. – has voted in favor of changing the childhood vaccine schedule.
On Thursday afternoon, the Advisory Committee on Immunization Practices, or ACIP, voted 8-3 to change the current recommendations that allow children under 4 to receive the MMRV vaccine, a combination shot for measles, mumps, rubella and chickenpox (or varicella).
The vast majority of children in the U.S. – about 85% – get separate shots for MMR and chickenpox, though parents currently have the option to give their children the single shot to cover all four diseases.
The panel's votes still require final approval from the acting CDC director Jim O'Neill, an ally of Secretary Kennedy's who's expected to greenlight their recommendations.
The MMRV vote will not affect the Vaccines for Children program – the committee decided to leave things as is for that program. That means it can still pay for these shots if parents opt to have them.
The panel, which advises the Centers for Disease Control and Prevention, also debated changes to the current recommendations for the hepatitis B vaccine. It will hold that vote on Friday, and several members including the chair Martin Kulldorff made comments supportive of the idea.
Also on Friday, the panel will vote on recommendations on who should be eligible for the latest COVID-19 vaccines.
The moves to overhaul the children's vaccine schedule represent the latest victory in Secretary Kennedy's long-running campaign to reshape policy. There was vocal opposition to the proposed changes from representatives of major medical groups who were present at the meeting.
"A question I've had all along through these discussions is why? Why are we addressing this hepatitis B vaccine recommendation? Is there really a reason?" asked Dr. Flor Muñoz, a pediatric infectious disease clinician who spoke at the meeting.
The proposed changes to the vaccine schedule also run counter to the hours of data presented by the CDC's own scientists throughout the meeting on the rationale for these recommendations.
Many in public health had warned that Kennedy was aiming to retool the vaccine schedule, after he replaced all 17 members of ACIP with his own hand-picked roster, including five members he added this week. Many of those he chose have a history of being critical of vaccines.
MMRV no longer recommended for kids under 4
Tension between the committee and the medical establishment surfaced throughout the discussion over changes to the MMRV vaccine guidance.
At issue was evidence, presented by CDC staff, showing a slightly increased risk of fever-related seizures in children ages 12-23 months after receiving the MMRV shot compared to the MMR, which concerned some committee members.
"I would go with the option that seems to be safer," said ACIP member Retsef Levi, an MIT professor of operations management who gained prominence during the pandemic for criticizing COVID vaccines.
But Dr. Cody Meissner, a pediatrician at Dartmouth College and ACIP member, pointed out that fever-related seizures, while "frightening" for the family, are not uncommon. They occur in 3% to 5% of all children.
"Every pediatrician is experienced in febrile seizures. We know that the prognosis is excellent," he said.
Removing the MMRV shots from the vaccine schedule for children under age 4 would spark more public confusion, compromise insurance coverage and potentially lead to fewer kids being vaccinated, said Dr. Jason Goldman, president of the American College of Physicians who is acting as a liaison to the committee.
"I urge this committee not to change the recommendations if they truly want to give the power to the parents to decide what is best for their child," he said.
Several liaisons from major medical groups criticized the committee's process.
Goldman said it failed to bring in the voice of subject matter experts, clinicians and patients, noting that the representatives from medical groups had been removed from ACIP workgroups.
A big break with existing policy on hepatitis B
The proposed changes to the hepatitis B vaccine schedule would mark a major departure – one that pediatricians and medical groups caution could reverse decades of progress in lowering rates of illness in the U.S.
Existing policy is to give the vaccine to all babies at birth regardless of the mother's hepatitis B status. The new recommendation would upend this, instead guiding doctors to screen all mothers and offer the vaccine only to those who do not test negative in an initial screening.
Several new ACIP members questioned why a universally given birth dose was necessary, if mothers could be adequately screened ahead of time.
"Are we asking our babies to solve an adult problem?" said Dr. Evelyn Griffin, an OBGYN and ACIP member, "Are we trying to lower the prevalence of hepatitis B in a high-risk population by vaccinating them on day one?"
But CDC scientists explained that gaps in prenatal screening could leave many babies vulnerable to catching a debilitating, sometimes fatal illness. And an infant could be infected by exposure to someone else in the household who is infected – around half of people with hepatitis B don't know they have it.
"I have not seen any data that says that there is any benefit to the infant of waiting a month, but there are a number of potential harms to the infants of waiting," responded Dr. Adam Langer, a CDC scientist who was presenting on the data.
Meissner echoed these sentiments, pointing out that efforts to identify high risk groups had failed in the past, which is why the recommendations were made in the first place.
"It's an extremely safe vaccine," said Meissner, "If we change the recommendations, we will increase the risk of harm based on no evidence of benefits because there will be fewer children who get the full hepatitis B series."
"We will be creating new doubts in the mind of the public that are not justified," he added.
Political tensions around the vaccine guidance process
The meeting comes on the heels of a contentious Senate hearing on Wednesday with the recently-ousted CDC director Susan Monarez.
Monarez testified that she was fired after clashing with Kennedy over his demands that she preemptively agree to approve vaccine recommendations from ACIP, and fire career scientists.
"He said the childhood vaccine schedule would be changing starting in September and that I needed to be on board with it," she said.
Kulldorff, an epidemiologist, acknowledged the "controversy" at the outset, with pointed comments against his critics – among them a slate of former CDC directors who have said the new members, selected by Secretary Kennedy, are "unqualified" and "share his dangerous and unscientific views. "
Kulldorf rebuffed the idea that he or others on the panel were "anti-vaxxers" and challenged the former directors to an "open public debate."
"If they want to be trusted, they should all accept," he said.
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