ACIP Meeting Opens With Focus on MMR and Varicella Vaccines Ahead of Key Votes

The Advisory Committee on Immunization Practices (ACIP) began its September 18 and 19 meeting today with a packed agenda centered on measles, mumps, rubella and varicella (MMRV) vaccines. ACIP, which advises the CDC on vaccine use in the United States, meets three times a year to review scientific evidence and vote on recommendations.

The meeting is currently being streamed on the CDC’s YouTube channel and is open for access by the public.

Today’s first half of the session introduced the five most recently appointed ACIP members to the overall panel of new faces updated earlier in June. The meeting also included representatives from federal agencies such as the CDC, FDA, CMS and NIH.

One notable absence was the American Academy of Pediatrics (AAP), which drew sharp criticism from ACIP member Cody Meissner, M.D., professor of pediatrics at Dartmouth Geisel School of Medicine, who was appointed in June 2025.

“I think it’s a grave mistake for the American Academy of Pediatrics not to participate in these discussions,” he said. “I think what the AAP is doing is moving themselves to irrelevance and the importance of the AAP is going to wane if they refuse to participate.”

The primary focus of the morning was MMRV vaccines.

CDC officials, including Arjun Srinivasan, M.D., and John Su, M.D., reviewed the dramatic decline in disease burden following the introduction of MMR and varicella vaccines.

Before vaccination, it was noted that measles caused hundreds of deaths annually, mumps was the leading cause of viral encephalitis and rubella led to devastating birth defects. Since the early 2000s, measles and rubella have been eliminated in the U.S., and varicella incidence has dropped by 97%.

However, safety concerns remain, particularly surrounding the MMRV combination vaccine.

Su presented evidence that children aged 12 to 23 months who receive the combined vaccine face a slightly higher risk of febrile seizures compared to those given MMR and varicella separately.

“Studies have identified an increased risk for febrile seizures during dose one of MMRV as compared with dose one of MMR plus varicella only during the one to two weeks after vaccination,” he shared.

However, he noted the risk disappears in older children receiving their second dose.

The committee is expected to vote later this afternoon on a draft recommendation that the combined MMRV vaccine not be used for children under age four, instead advising providers to administer MMR and varicella separately for the first dose. Combination use would still be allowed—and typically be preferred—for the second dose between ages four and six.

The session also touched on anticipated votes regarding hepatitis B vaccines.

As shared by the ACIP September 17, the proposed changes include universal hepatitis B testing for pregnant women and delaying the first pediatric hepatitis B dose until one month of age if the mother tests negative. These items are slated for discussion in the second half of today’s agenda.

Throughout the morning, ACIP Chair Martin Kulldorff, M.D., made a point to address speculation about the committee’s stance on vaccines.

“The members of this ACIP committee are committed to reassuring the public and restoring public confidence by removing unnecessary risk and harms whenever possible. That is a pro-vaccine agenda,” he said in response to a Senate Finance Committee meeting that expressed their concern the new ACIP committee was made of vaccine skeptics. “False accusations that we and other respectable vaccine scientists are unscientific and dangerous anti-vaxxers just add legitimacy to anti-vax positions.”

The first half of the day concluded with debate over how new recommendations might impact parental choice and clinical practice.

Jason Goldman, M.D., an internal medicine specialist and president of the American College of Physicians, cautioned the panel by stating the recommended vaccine changes are “taking away the choice of parents to have informed consent and might want to do for the health benefit of their children. So I urge this committee not to change the recommendations if they truly want to give parents that choice.”

ACIP is expected to finalize votes on both MMRV and hepatitis B vaccines by the end of the day. Friday’s session, the second day of the meeting, will change course and focus on COVID-19 vaccines.