A key advisory group to the U.S. Centers for Disease Control and Prevention (CDC) is meeting this week to decide whether newborns should continue receiving a hepatitis B vaccine within 24 hours of birth—an extraordinary move that could alter guidance that has shaped pediatric care since the early 1990s.

For more than three decades, doctors in the United States have been urged to administer the hepatitis B vaccine to every newborn on the day they are born, a policy credited with reducing severe childhood hepatitis B infections by 99%. The virus, which can be passed from mother to baby during childbirth, can cause lifelong liver damage, and there is no cure.

However, the long-standing consensus is now being questioned by some members of the CDC’s Advisory Committee on Immunization Practices (ACIP).

Dr. Kirk Milhoan, a pediatric cardiologist from DeTar Healthcare System in Texas and the newly appointed ACIP chair, told NBC News that he is concerned the birth dose may cause “neonatal fever,” potentially prompting unnecessary testing in newborns. His appointment earlier this year followed the removal of the previous committee by Health Secretary Robert F. Kennedy Jr., adding to the heightened scrutiny surrounding this review.

Many pediatric experts strongly disagree with any move to delay or remove the birth dose. Representing the American Academy of Pediatrics (AAP), Dr. Sean O’Leary said he has “never once seen a fever actually associated with hepatitis B vaccine” during his care of “thousands of babies.” His view is supported by extensive scientific literature.

A new analysis released Tuesday by the Vaccine Integrity Project, reviewing more than 400 studies, found no evidence of harm from the birth dose. The report estimated that newborn vaccination has prevented over 6 million infections and nearly 1 million hospitalizations, although the analysis has not yet undergone peer review.

ACIP is expected to vote later today or tomorrow. The committee could vote to maintain the current guidance, delay the first dose by several weeks, or withdraw the recommendation entirely. Even if the birth dose is no longer recommended, physicians could still offer the vaccine; however, insurance coverage typically follows CDC guidance, meaning the vote could significantly influence practice.

Public health experts warn that removing or delaying the birth dose could have serious consequences. Without vaccination, up to 90% of infants exposed to hepatitis B during childbirth develop chronic infection, according to the AAP. Identifying which babies are truly at risk is also challenging. Not all pregnant women receive consistent prenatal care, and some may be reluctant to disclose risk factors. A 2019 report found that only 84% to 88% of pregnant women were screened for hepatitis B.

Milhoan has suggested that parents must be forthcoming about their risks, saying, “I hope they love their baby more than they love their pride.” His comments, along with his history of questioning multiple vaccines—including COVID-19 shots—have raised concerns among some vaccine experts. Although he has highlighted the rare myocarditis risk after COVID vaccination in young men, multiple studies have shown the condition is more common after COVID infection than after the vaccine.

The ACIP meeting will also evaluate data on aluminum adjuvants, which are used in several vaccines to boost immune response. A recent study involving more than one million people found no association between aluminum-containing vaccines and chronic diseases or autism.

The review comes at a turbulent moment for the CDC. On November 19, the agency quietly revised a webpage that previously stated unequivocally that vaccines do not cause autism, softening the language in a move that has drawn widespread attention from scientists and public health advocates. 

Despite the change, scientific evidence continues to show no link between vaccines and autism.

As the ACIP prepares to cast its vote, the outcome could reshape how the nation protects its youngest children from a potentially deadly virus—reviving a debate many believed had long been settled.