In a perplexing conclusion to an oftentimes tense meeting of the Centers for Disease Control and Prevention's (CDC’s) Advisory Committee on Immunization Practices (ACIP) Thursday, the panelists—assembled recently in the aftermath of Robert F. Kennedy Jr.’s purge of the committee—seemed to contradict themselves when it came time to vote on a vaccine recommendation.
Asked whether the U.S. pediatric vaccine schedule should be updated to not recommend Merck’s combined measles, mumps, rubella and varicella (MMRV) to children before the age of 4, the ACIP members voted 8 to 3, with one abstention, in favor of the change. The recommendation leaves room for children to receive an MMR shot and a varicella vaccine separately as their first dose in a two-vaccine sequence.
But on a second voting question about whether that decision should apply to the coverage framework under the nation’s Vaccines for Children (VFC) program, the panelists backpedaled, issuing 8 "no" votes and just one vote in favor of the change.
Then, at the beginning of Friday’s meeting, the ACIP members moved to recast their decisions on Thursday’s second voting question around VFC coverage of the MMRV vaccine. The results of the mulligan yielded 9 "yes" votes and 3 abstentions, reversing the decision the panelists had previously issued.
The ACIP’s recommendations still need to go before the CDC for final approval.
Three members of the panel abstained from voting on the second question. While one of those panelists, Robert Malone, M.D., had to recuse himself due to his role in a prior lawsuit, the other two panelists who held back votes cited confusion over the implications of their ballots and why they would be able to vote to uphold coverage on a vaccine that is no longer recommended under the first decision.
In a note to clients after the vote, analysts at Citi pointed out that the updated recommendation doesn't change guidance around childhood MMRV vaccination in general, although it does impact parents' choice in the matter. The move could impact Merck's vaccine specifically, but the analysts said they expect that total vaccination rates for the four diseases "are likely to remain stable."
The confusion-riddled voting process marked the end of a frequently heated meeting, in which a theme of distrust seemed to pervade the proceedings. The ACIP was also set to vote on whether to uphold universal hepatitis B virus (HBV) vaccination recommendations for infants at birth, but the question was tabled until Friday, when the panel was also slated to weigh in on COVID-19 vaccine recommendations.
Friday morning, the committee scrapped the HBV vote altogether.
Among the many questions broached during Thursday's ACIP meeting, one that resonated strongly with many of the health association liaisons sitting on the sidelines of the event—as well as several of the panel members themselves—was what prompted the voting questions on Thursday’s agenda, and why now?
Many of those medical organizations that previously assisted the CDC in setting vaccine recommendations were recently iced out. The groups included organizations like the American Academy of Family Physicians, the American Academy of Pediatrics, the American College of Physicians and the American Geriatrics Society.
Up until last month, those liaisons participated in ACIP work groups that reviewed relevant published and unpublished data and developed recommendation options for presentation to the committee. At Thursday's meeting, the liaisons were allowed to participate during discussion periods but did not work directly with ACIP members prior to the meeting.
A certain level of mistrust ran throughout the confab, whether in regard to the liaisons’ scrutiny of the ACIP’s motives or many of the panelists’ openness to the data presented by the CDC.
The voting question on the MMRV vaccine came down to the risk of febrile seizures in kids who receive the quadruple combination shot as the first of two childhood doses. The previous recommendation from ACIP advised parents and doctors to discuss which vaccine—either the MMRV shot or an MMR vaccine and a separate varicella shot—was most appropriate for their child’s first dose.
The quadruple shot makes up just 15% of the first doses given in the MMRV sequence in the U.S., the CDC pointed out in a presentation (PDF) on the present immunization landscape, citing 2024 data from 39 separate jurisdictions’ Immunization Information Systems.
During the proceedings, many ACIP members brought the issue back to informed consent and the rising tide of vaccine hesitancy in the U.S., frequently straying from the voting questions and data at hand. The committee’s chair, Martin Kulldorff, Ph.D., questioned whether instances of febrile seizures in children receiving the MMRV vaccine as their first dose might affect further uptake of that shot or immunizations in general.
Another panelist, Evelyn Griffin, M.D.—newly added to ACIP as of this week—said that it was “difficult to decipher the risk” of the MMRV vaccine since trials compared it to existing immunizations, rather than a true placebo. Griffin caveated that she understood it’s typically considered unethical to run a placebo-controlled vaccine trial when a safe and effective shot already exists but suggested that such a study would probably be “the most ethical thing to do in a day and age where parents are, through full informed consent, not getting their children vaccinated.”
Representatives from the CDC quickly countered, however, that it would in fact be unethical to run a placebo-controlled MMRV trial “at a time where we’re seeing the highest measles cases we’ve seen in many years.”
Meanwhile, panelist Cody Meissner, M.D., who’s the only current ACIP member to have sat on the committee before, sought to clarify for his voting peers that febrile seizures are common, pediatricians are well-equipped to handle them and that the “prognosis is excellent,” while admitting that the main issue is the anxiety these events can cause parents.
Getting back to the heart of why ACIP had been assembled this week, Meissner said he wasn’t sure if “putting limited resources into this activity will give us the greatest bang for the buck.”
Meanwhile, in an attempt to play devil’s advocate, Meissner suggested that the voting question implies ACIP “doesn’t trust parents to make a decision,” adding, “if a parent wants to get a single dose, why are we taking that away?” He voted ‘No’ on changing ACIP’s previous MMRV vaccine recommendation.
That sentiment was rampant among the health association liaisons sitting in on the meeting, as well.
“I would argue that this decision is going to create more confusion among the public,” said Jonathan Goldman, M.D., of the American College of Physicians. “It does not involve the aspect of actual practicing clinicians and how we deal with vaccine hesitancy and how we talk to our patients, and also, when you make this recommendation, you now give license to insurance companies and the Vaccines for Children program not to cover this vaccine.”
Meanwhile, the Society for Adolescent Health’s Amy Middleman, M.D., stressed to the ACIP members that “it’s important to talk about what the evidence shows versus what people may believe that is not necessarily supported by the evidence.”
Middleman went as far as to question why a vote on the MMRV issue was needed at all.
“I haven’t heard any information about urgency related to this decision,” she said. “I’m not sure why it has to be made today. I would urge the committee to follow the methodical process of an evidence-to-recommendation process before voting on something that affects public health to this degree.”
Editor's note: This story has been updated with additional detail from Friday's meeting.