In a significant move that signals Health Secretary Robert F. Kennedy Jr.’s intention to overhaul the standard childhood vaccination schedule, federal advisors gathered on Thursday. They are expected to vote against recommending the combined measles, mumps, rubella, and chickenpox (MMRV) vaccine for children under four.
While this particular decision from the Kennedy-appointed committee may not immediately alter widespread practice—as separate shots for these diseases are already more common and their recommendations remain firm—it represents a foundational shift.
This vote is anticipated to be just the initial step in a series of revisions to the official immunization guidelines.
During Thursday’s session, Martin Kulldorff, chair of the Advisory Committee on Immunization Practices (ACIP), announced the formation of two new work groups: one dedicated to examining vaccine use during pregnancy, and another focused on thoroughly reviewing existing childhood and adolescent vaccination schedules.
This comprehensive review has deeply concerned many public health experts, who worry that restricting access to specific vaccines could lead to the re-emergence of diseases that were once largely eradicated.
Furthermore, the committee is poised to vote on limiting the hepatitis B vaccine, a critical defense against a liver-damaging infectious disease. The proposed change suggests administering this vaccine only to newborns whose mothers are confirmed carriers, or to other infants who have reached at least one month of age.
Dr. Sean O’Leary, who chairs the infectious disease committee for the American Academy of Pediatrics, warned, ‘If children lose access to these vaccines, we risk seeing the return of serious diseases that once plagued childhood.’
He emphasized the tragedy of preventable suffering, stating, ‘These diseases are almost entirely avoidable today, and it’s heartbreaking for a pediatrician to witness a child and family endure such illness.’
An accompanying graphic illustrates the current childhood vaccination schedule, highlighting the specific shots under review by the CDC’s immunization advisory panel for children under 18. These include: Hepatitis B (1st and 2nd doses), Covid-19 (for 6 months), and Measles, Mumps, Rubella, Varicella (MMRV) at 12 months and 4 years (as an alternative to separate MMR and Varicella shots). The graphic notes the start of the age range for each recommended dose.
Introduced in 2005, the MMRV vaccine offers a single-shot alternative to the separate MMR (measles, mumps, rubella) and varicella (chickenpox) immunizations.
During their initial meeting in June, panelists had already signaled their strong intent to scrutinize the MMRV vaccine.
On Thursday, data presented by Centers for Disease Control and Prevention (CDC) scientists indicated that the combined MMRV vaccine carries a slightly elevated risk of fever-induced seizures. It was noted that such seizures are generally harmless and can also occur with common childhood ailments like ear infections.
The CDC has historically advised administering MMR and chickenpox vaccines separately for children under four, precisely due to this risk of fever-related seizures.
Despite this, some pediatricians and parents preferred the combined MMRV shot to reduce the number of clinic visits and injections. The committee’s impending vote aims to remove this option.
Medical organizations outside the committee have voiced strong objections to the proposal to recommend against this vaccine.
Dr. Amy Middleman, head of pediatrics and adolescent medicine at Case Western Reserve University and a liaison to the committee, noted that the MMRV discussion lacked customary detailed presentations on feasibility, acceptability, cost-benefit analysis, or equity concerns.
A recommendation against the MMRV vaccine would have significant financial implications, potentially removing it from coverage by the Vaccines for Children Program and the Children’s Health Insurance Program, which together serve about half of the nation’s children.
Dr. Middleman urged the committee to adhere to a thorough, evidence-based recommendation process before making decisions with such broad public health impact.
Earlier, Susan Monarez, who served as CDC director for less than a month before her ousting, informed lawmakers that Health Secretary Kennedy intended to revise the childhood immunization schedule.
Monarez testified that Kennedy had instructed her to approve all panel recommendations ‘regardless of the scientific evidence’ presented.
Historically, the advisory panel’s decisions have shaped state vaccine mandates and ensured insurance coverage. However, its recent actions seem to have undermined its authority and credibility.
Following the committee’s inaugural meeting in June, several prominent medical organizations ended their long-standing collaboration with the panel, opting to issue their own independent recommendations.
Adding to the concerns, most major insurers announced on Tuesday that they would continue to cover routine immunizations through 2026, irrespective of any restrictive votes by the panel. Senator Bill Cassidy, a Republican and chair of the Senate health committee, explicitly stated on Wednesday that Americans should be wary of the panel’s vaccine recommendation revisions.
The MMRV discussion brought underlying tensions among the panelists to the forefront.
Dr. Cody Meissner, a pediatrician from the Dartmouth Geisel School of Medicine and a highly respected expert in vaccine science, expressed his concern: ‘What we’re essentially saying is that we don’t trust parents to make these decisions.’
He warned that if the panel votes against the combined vaccine, ‘the shot won’t even be an option’ for families.
Notably, most of the current panelists are new appointments. In June, Kennedy controversially dismissed all 17 previous committee members, replacing them with seven new individuals who largely align with his skeptical views on vaccines. He announced five more appointments just this week. Traditionally, ACIP members undergo a rigorous vetting process lasting months or even years.
During their initial June meeting, the seven new panelists declared their intention to meticulously examine all recommended childhood and adolescent vaccinations. They also voted to revoke a long-standing recommendation for certain flu shots containing thimerosal, a preservative falsely linked to autism by anti-vaccine advocates.
Further changes are anticipated for hepatitis B vaccine recommendations. This vaccine’s first dose is typically administered to newborns within 24 hours, a practice public health experts credit with drastically reducing maternal transmission in the U.S. — from approximately 20,000 cases annually before 1991 to fewer than 20 today.
Untreated hepatitis B poses a severe threat, potentially causing liver damage, cirrhosis, liver failure, and liver cancer. Infants infected at birth face a 90% chance of developing chronic hepatitis B, with one in four experiencing severe complications or death.
Kennedy and his supporters have asserted that hepatitis B is exclusively transmitted through sexual contact or shared needles, suggesting that only infants born to infected mothers require immunization at birth.
Dr. Noele Nelson, a lead author of the existing hepatitis B vaccine guidelines and former head of the CDC’s hepatitis vaccines work group, pointed out that a pregnant woman’s hepatitis B status might not always be accurately known.
She added that infections could be missed due to inaccurate test results or issues with reporting and interpreting them.
Dr. Nelson, who resigned from the CDC in July, concluded that ‘universal hepatitis B vaccination at birth acts as an effective safety net, protecting infants whose mothers’ infection status is unknown or inaccurately recorded.’
Dr. James Campbell, vice chair of the infectious disease committee for the American Academy of Pediatrics, clarified that hepatitis B is a highly contagious virus that can spread through various means beyond sexual contact, including shared household items like toothbrushes, razors, or combs.
He recalled that previous risk-based vaccination recommendations, focusing solely on infants of infected mothers, failed to significantly reduce the disease’s overall impact. ‘That’s why we now have a universal recommendation,’ he explained.
Kennedy has repeatedly cast doubt on the hepatitis B vaccine’s safety, incorrectly asserting that it lacked proper testing. During his January confirmation hearing, he notably refused to affirm the scientifically accepted fact that the hepatitis B vaccine does not cause autism.
Conversely, Dr. Claudia Hawkins, a specialist in hepatitis B and C at Northwestern University Feinberg School of Medicine, affirmed the vaccine’s strong safety record, stating, ‘Hepatitis B vaccines are very safe, with no reports of any serious side effects in babies, children, or adults since their introduction.’
She emphasized, ‘There is no medical reason to delay the hepatitis B vaccine.’
A distinct vote regarding Covid-19 vaccines is slated for Friday.
Correction: An earlier version of this article incorrectly stated that AHIP, the health insurance industry’s national trade association, announced on Wednesday, Sept. 16, 2025, that health plans would continue to cover all immunizations. The correct date for this announcement was Tuesday, Sept. 16.
Apoorva Mandavilli is a science and global health reporter, specializing in infectious diseases, pandemics, and the public health organizations tasked with their management.