The Centers for Disease Control and Prevention's vaccine advisory panel met Thursday for the first of two days of discussions about childhood vaccine schedules and recommendations. The panel is focusing on the hepatitis B vaccine and plans to vote on whether to continue recommending it be given to all children at birth or delay the first dose.

However, that vote was postponed until Friday amid confusion on the exact wording of the questions the committee was set to vote on.

The hepatitis B vaccine has been universally recommended for newborns in the U.S. since 1991. Since then, research shows hepatitis B infections among infants and children have dropped 99%.

Hepatitis B is an incurable infection that can lead to liver disease, cancer and early death.

The shot has become a target of vaccine skeptics, including Health and Human Services Secretary Robert F. Kennedy Jr., who falsely claimed on a podcast in June that the birth dose is a "likely culprit" in autism. Kennedy has appointed all of the members of the Advisory Committee on Immunization Practices, or ACIP, during his tenure as HHS secretary.

Here's what to know about the meetings and the hepatitis B vaccine.

What happened at Thursday's ACIP meeting?

The panel postponed until Friday its plans to vote on whether or not to continue recommending the first dose of hepatitis B vaccine be given within 24 hours of birth — known as the birth dose.

At one point in Thursday's session, committee member Dr. Joseph Hibbeln said that the group had seen three different versions of questions to vote on in the past 72 hours. A technical issue prevented the new voting language from being put up on slides. The presentation was later moved to the end of the agenda, to be displayed just before the vote. There were questions of how many questions members would be asked to vote on. There were no hard copies of the language available.

"We're trying to evaluate a moving target," Hibbeln said.

Similar confusion pervaded ACIP's September meeting, when members admitted they didn't know what they were voting on when they rejected a combined measles-mumps-rubella-chickenpox vaccine before voting to keep it funded, then reversing the funding vote the next day.

A motion to delay the vote until Friday morning was agreed upon by a 6-3 margin.

The meeting was contentious at points. Vicky Pebsworth, the ACIP Childhood and Adolescent Immunization Schedule Workgroup Chair and a regional director of the National Association of Catholic Nurses, said in introductory remarks that the panel was reviewing the vaccine because of "concerns raised by some groups."

Panel members presented information on the prevalence of acute and chronic hepatitis B, and discussed transmission and safety data. Former board members and liaisons to medical organizations sharply criticized the presentations and said some data was mischaracterized.

Dr. Jason Goldman, liaison to the ACIP for the American College of Physicians, called the meeting "completely inappropriate" and accused the panel of "wasting taxpayer dollars by not having scientific, rigorous discussion on issues that truly matter." Goldman also highlighted that the hepatitis B birth dose is not mandated and that parents are encouraged to make decisions in consultation with their doctor.

Why is the hepatitis B vaccine given to newborns?

The hepatitis B virus is primarily transmitted through blood and bodily fluids and is highly contagious. The virus can also survive on surfaces for a week; research shows it can be transmitted through indirect contact with infected fluids.

Hepatitis B can be passed from mother to child and can also be transmitted to infant children by caregivers, according to the American Academy of Pediatrics.

Infected adults often have few to no symptoms and can spread it without even knowing they have the virus. The CDC has estimated that of the 2.4 million people in the U.S. with hepatitis B, about half do not know they are infected.

When the hepatitis B vaccine is given to newborns soon after birth it is up to 90% effective at preventing infection from the mother. If babies receive the full three-dose vaccination series, 98% of them have immunity from the illness, according to the AAP.

Newborns who become infected with hepatitis B at birth and infants who contract the virus within the first year of their life have a 90% chance of developing chronic hepatitis B, an illness that can cause life-threatening issues including cirrhosis, liver failure and liver cancer. About 25% of those patients end up dying prematurely as a result.

Previously, prenatal screening for hepatitis B was targeted to women at higher risk, including those with multiple partners or who injected drugs, and the vaccine was only recommended for infants born to those who tested positive for the virus. But that approach failed to identify many infections, researchers found, and even with universal testing during pregnancy some "leakage" cases continued to occur.

The CDC still recommends that pregnant women get tested for hepatitis B, but about 16% of expecting mothers fall through the cracks, according to the agency.

"The birth dose has served as a critical safety net in the U.S. healthcare system — to protect against gaps in prenatal screening, missed HBV [hepatitis B virus] diagnoses, communication errors, and inconsistent follow-up," according to the Vaccine Integrity Project of the University of Minnesota's Center for Infectious Disease Research and Policy.

Parents are not mandated to give their children the hepatitis B vaccine, though many schools and child care facilities currently require the shots.

The birth dose and vaccine series have helped keep rates low in recent years. In 2021, CDC data showed about 17,827 children were born to mothers who tested positive for hepatitis B, but there were only 17 reported cases of newborns contracting the virus from their mothers that year, the AAP said. The pediatricians' organization credited the birth dose for that progress.

What do experts say about the hepatitis B vaccine?

Medical experts and organizations including the American Academy of Pediatrics and the American Medical Association say extensive research shows that the hepatitis B vaccine is safe. It has a long track record, and multiple studies show the shot is not associated with an increased risk of infant death, fever or sepsis, multiple sclerosis or autoimmune conditions. Severe reactions to the vaccine are rare, with the main adverse events reported being crying and fussiness that pass quickly.

"The hepatitis B vaccine has ... one of the most well established safety records of any vaccine, and it's one of our best. We've been using it for a long time. It's one of our best tools to protect babies from chronic illness and liver cancer," Dr. Sean O'Leary, chair of the Committee on Infectious Diseases for the American Academy of Pediatrics and an assistant professor of pediatrics at the University of Colorado School of Medicine, told CBS News. "This is a situation where one missed case is too many."

As O'Leary put it to KFF Health News: "No one expects to get in a car wreck, right? And yet we all put our seat belts on. This is similar."

Sen. Bill Cassidy, a Louisiana Republican who chairs the Senate Committee on Health, Education, Labor and Pensions, and who is also a physician whose medical practice focused on hepatitis B, says the at-birth vaccine dose has "decreased incidence of chronic hepatitis B by 20,000 people over the last two decades." He said he was "very concerned" about a potential change in the recommendations.

"I'm a doctor. I have seen people die from vaccine-preventable disease," Cassidy said on "Face the Nation with Margaret Brennan." "I want to make America healthy, and you don't start by stopping recommendations that have made us substantially healthier."

On Thursday morning, as the ACIP meeting began, Cassidy criticized the panel on social media.

"The ACIP is totally discredited," he wrote. "They are not protecting children."

What can be expected at the ACIP meeting?

The ACIP meeting will span two days. In addition to discussing and voting on the hepatitis B birth dose recommendation, the panel will discuss childhood vaccine schedules. There is no vote planned for the latter topic.

A vote about the hepatitis B vaccine was scheduled for Thursday, according to a meeting agenda, but later postponed until Friday. The agenda also included time for multiple presentations and discussions on the topic, as well as time for public comments.

"This week marks the third meeting of this revised, this new ACIP committee," O'Leary told CBS News, referring to the RFK Jr. appointees. "The last few meetings have been deeply alarming, riddled with falsehoods, and I think unfortunately, we can expect the same with this meeting this week."

The panel debated moving the birth dose to one month of age in their September meeting, but tabled the topic.

What could happen if the hepatitis B vaccine recommendations are changed?

The ACIP's recommendations go to the CDC director for approval and adoption as policy. Ultimately, decisions are left to the states, which tend to base their policies off the CDC's guidelines but can choose to set their own. The panel's recommendations also carry weight with insurance companies. Most private insurers are required to cover vaccines recommended by the panel. If ACIP changes its recommendation, coverage for hepatitis B vaccines may change.

Doctors say they're concerned that any decision to delay the first dose or weaken the recommendations would result in more infections — meaning more lives burdened by disease or cut short.

"Delaying the first hepatitis B vaccine dose beyond the newborn period introduces risks that have lifelong detrimental consequences and no measurable health benefit," three leading infectious disease specialists write in an article published Wednesday in JAMA, the Journal of the American Medical Association.

They note that over the years, "randomized trials, safety monitoring, and large cohort studies have consistently confirmed the vaccine's safety," and researchers say there is no evidence of any safety benefit in waiting until a child is a month old.

"If you wait a month and if the mom happens to be positive, or the baby picks it up from a caregiver, by that time the infection is established in that baby's liver," Dr. William Schaffner, a professor of preventative medicine at the Vanderbilt University School of Medicine and a former voting member of ACIP, told KFF Health News. "It's too late to prevent that infection."

That would result in the virus circulating at higher rates and increase the risk of contracting it for everyone, Schaffner said. More hepatitis B cases would also mean higher costs for patients and the medical system overall.

"There's no reason to delay or space out vaccines," O'Leary said. "Doing so just puts children at risk."

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