Updated at 11:08 a.m. on September 19, 2025
Three months into its tenure, in a muddled and chaotic meeting, Robert F. Kennedy Jr.’s handpicked vaccine advisory committee managed to take down one of its planned targets.
On Thursday, its members voted to limit the national guidance for a childhood vaccine that has helped protect infants against some of the most dangerous and fast-spreading viral diseases in the United States. If the CDC adopts the committee’s advice, the agency will no longer recommend the combination measles-mumps-rubella-varicella (MMRV) vaccine for kids younger than 4, defaulting their first dose of protection against MMR and chickenpox to two separate shots.
But although the committee also discussed delaying the first dose of the hepatitis-B vaccine from birth to at least one month old for most infants, it could not take a clear swing at revising the current recommendations. Instead, it decided to table any vote on that vaccine.
The committee’s focus on these two vaccines seems to be an agenda of Kennedy’s own design. In the past, the panel, known formally as the Advisory Committee on Immunization Practices, or ACIP, has considered changes in guidance prompted by evidence—a new shot being brought to market, the release of new data on a vaccine’s effectiveness or safety. Now Kennedy himself is driving much of what the committee discusses, including Thursday’s deliberations on hepatitis B and MMRV, Demetre Daskalakis, the former director of the CDC’s National Center for Immunization and Respiratory Diseases, told us. “Those were dictated topics,” he said. (A spokesperson for the Department of Health and Human Services told us via email that Susan Monarez, the most recent CDC director, approved the agenda before she was fired last month. Monarez did not respond to a request for comment.)
These vaccines are among the most vulnerable to challenge on the grounds that they appear more risky or seem less necessary than the rest of the immunizations the CDC recommends. Some other high-income countries, for instance, do not recommend the hepatitis-B vaccine universally at birth; MMRV vaccines have been linked to an increased risk of certain side effects in children under 2. Helen Chu, an infectious-disease specialist at the University of Washington, sees no reason to alter the recommendations for these vaccines, but can imagine how they’d fit into a broader strategy, she told us: “If you were going to pick, these are good ones to pick off first.” (Chu was a member of ACIP until Kennedy abruptly dismissed her in June along with the other 16 sitting members.)
The committee may have kept the recommendation for hepatitis-B vaccines intact for now. But each revision to the national immunization schedule makes it that much easier for Kennedy’s ACIP to cast other vaccines as dispensable. “It’s more the principle,” Daskalakis said at The Atlantic Festival on Friday—“that they, with no data, with no reason to do it, have just removed a vaccine from the pediatric schedule.”
To Margot Savoy, a senior vice president at the American Academy of Family Physicians, this looks like “a very calculated approach.” (The AAFP is one of several professional medical societies that recently published vaccine recommendations that openly diverge from the CDC’s in response to Kennedy’s overhaul of U.S. vaccine policy.) Many of Kennedy’s initial attacks against immunizations have focused on COVID vaccines, capitalizing on lingering and highly politicized resentment over pandemic-era policies. And in June, at the first meeting of Kennedy’s newly reconstituted ACIP, the committee voted to drop its recommendations for flu vaccines containing the mercury-based preservative thimerosal—a decision that played on decades-old fears, fueled by anti-vaccine activists, that the compound can cause harm, despite years of evidence showing that it doesn’t.
Those early decisions were relatively limited in their impact. Last flu season, fewer than 5 percent of flu vaccines in the U.S. contained thimerosal. COVID-vaccine uptake had already been declining for years and was never very high among children; the previous iteration of ACIP was already considering paring back some of the recommendations for COVID vaccines before Kennedy fired all the sitting members. But those restrictions also paved the path for this week’s votes, which will limit the country’s options to protect its children in the years to come.
In an email, the HHS spokesperson defended Kennedy’s ACIP, writing that the committee “is guided by gold standard science and will make any recommendations based on the totality of evidence presented to them. HHS has not, and will not, limit access to vaccines.”
Compared with MMR and varicella vaccines that are administered separately, MMRV vaccines do have a higher risk of febrile seizures (which, while frightening to watch, usually resolve on their own and don’t generally carry long-term risks). The CDC once recommended MMRV over separate shots, but as the data on seizures emerged, the agency shifted its guidance to prefer giving the first dose of the MMR and varicella vaccines separately. Several ACIP members suggested on Thursday that the vaccine and its side effects were still poorly understood, and that safety issues would crater trust in vaccines overall.
But the experts we spoke with pushed back on that notion. The CDC previously kept MMRV as an option in part to offer more choices for families—especially ones that don’t interact regularly with the health-care system or prefer fewer injections. Edwin Asturias, a pediatrician at the Colorado School of Public Health and one of the ACIP members Kennedy dismissed in June, told us. Each year, about 10 percent of families opt to give MMRV as their child’s first dose, a spokesperson for the pharmaceutical company Merck, which manufactures the vaccine, told us. Removing that option, experts said, could dissuade some families from vaccinating their children against those viruses at all.
ACIP also considered MMRV’s status in the Vaccines for Children program, which offers shots to millions of families that can’t afford them. In a confused and extremely unusual series of votes on Thursday evening and Friday morning, the committee voted first to preserve MMRV in the program, then to remove it; the children eligible for that program—roughly half of American kids—can now no longer receive it before age 4.
While discussing the hepatitis-B vaccine—which Kennedy has refused to say doesn’t cause autism, even though studies show no association—some committee members spent hours casting doubt on the vaccine’s safety, despite being shown again and again strong evidence that it’s one of the safest shots made today. “I’m just not sure I see the data that suggests: Where is the benefit?” Retsef Levi, one of the ACIP members, said. Martin Kulldorff, the committee’s chair, also pushed CDC officials to compare the U.S. vaccination schedule with those of other developed nations that don’t recommend a universal birth dose.
But the discussion was punctuated by heated pushback from other meeting attendees, including liaisons from multiple professional medical societies, CDC officials, and the minority of ACIP members that has voted against substantial changes to the immunization schedule. They pointed out that other wealthy nations that skip the universal dose at birth also differ from the U.S. in other ways—universal health care, higher hepatitis-B screening rates, and better prenatal care. In the U.S., about 12 to 16 percent of pregnant women are never tested for the virus at all. Babies can also contract the highly infectious pathogen shortly after birth from family members, caregivers, children, and even surfaces. “I have not seen any data that says that there is any benefit to the infant of waiting a month,” Adam Langer, a CDC official who presented background information about hepatitis B shots, said during the meeting, “but there are a number of potential harms.”
On Friday morning, the entire committee, except for Kulldorff, voted to table any decision about this vaccine. “There’s enough ambiguity here and enough remaining discussion about safety, effectiveness, and timing that I believe that a vote today is premature,” Robert Malone, one member of the committee, said. ACIP did not specify when the matter would be raised again.
Still, the committee made its choice about MMRV at breakneck speed. In advance of meetings, ACIP has typically assembled work groups that would evaluate the evidence on vaccines, then share their analyses with their colleagues and the public. Major decisions would not be made without an assessment of the benefits and risks of each option. All of that has gone out the window. Experts from professional societies, in the past invited to advise committee members, have been barred from participating in work groups; five committee members were added to ACIP just days before the meeting. At a Senate hearing yesterday, Debra Houry, who resigned recently as the CDC’s chief medical officer, told senators that she was discouraged by a senior adviser at the agency from providing data or asking questions about changes to the hepatitis-B recommendation.
This ACIP, experts pointed out, seems uninterested in discussing vaccines’ benefits. Instead, it has been building the case that many vaccines pose excessive risk, and that the U.S. is pushing far more of them than are necessary. The intention seems to be to “cast the previous committee as less concerned about safety than they are,” Kelly Moore, a former ACIP member and the president of Immunize.org, a nonprofit supporting immunization, told us. They appear to be suggesting that the CDC has saddled the public with an unsafe, bloated vaccine schedule that Kennedy’s chosen cohort will now fix.
These early shifts—less COVID vaccination; fewer options for flu, MMR, and chickenpox vaccines—may seem benign enough. But that may be part of the point. Kennedy and his allies are testing the waters, but they’re also accustoming the public both to the idea of fewer vaccines and to the routine of doubting vetted immunizations. The more logical their early choices seem, the more reasonably Americans might assume the ones that follow are too. “By the time people realize we’re in a bad way, we’re going to be so far in a bad way, we won’t be able to get back out,” Savoy told us. Whether vaccine infrastructure disappears by erosion or rapid demolition, the end result will be the same: a nation far less protected than it once was and could still be.
