The hepatitis B vaccine has recently become a controversial topic as Health Secretary Robert F. Kennedy Jr. continues to express concerns about vaccine safety.

Newborns typically receive the vaccine shortly after birth because hepatitis B, an incurable infection that can lead to severe liver complications and even death, can be transmitted during childbirth.

During a Senate Finance Committee meeting with Kennedy on Thursday, Sen. Roger Marshall, R-Kan., voiced his opinion that giving the hepatitis B vaccine to all newborns is questionable, particularly when the mother tests negative for the virus.

Marshall, an OB-GYN with experience in delivering 5,000 babies, supports vaccinating newborns of mothers who have not undergone prenatal care or hepatitis B testing but doubts the necessity of universal vaccination.

He’s not the only Republican senator who’s been critical of the vaccine.

“No medical reason to give newborns Hep B vaccine if the mother is not infected. All mothers who deliver in a hospital are tested,” Rand Paul of Kentucky commented on X last week.

That prompted Sen. Bill Cassidy, R-La., to respond.

“Empirically, this is not accurate. Not all mothers receive prenatal care,” Cassidy responded. “Some might contract the infection between their initial first trimester testing and delivery. Occasionally, the test is overlooked.”

Both Paul and Cassidy are physicians; Paul is an ophthalmologist and Cassidy is a gastroenterologist who has treated hepatitis patients.

The issue isn’t likely to fade away anytime soon: Next week, a committee that advises the Centers for Disease Control and Prevention on vaccines is slated to discuss the hepatitis B vaccine. Kennedy fired all 17 members of the previous committee in June and handpicked seven replacements, several of whom have expressed anti-vaccine views.

The new committee chair, Martin Kulldorff — a biostatistician who said he was fired from Harvard for refusing to get a Covid vaccination — cast doubt on the hepatitis B vaccine at the group’s first meeting in June.

“Unless the mother is hepatitis B positive, an argument could be made to delay the vaccine for this infection,” Kulldorff said.

That argument includes dangerous assumptions, said Chari Cohen, president of the Hepatitis B Foundation. A 2019 report found that only 84% to 88% of pregnant women are tested for the virus.

Hepatitis tests aren’t perfect and sometimes produce false results, Cohen said. And pregnant women may not tell their doctors about their past or current behavior for fear of stigma. The virus can spread through sexual contact or sharing needles for injecting drugs.

Without vaccination, 90% of babies exposed to the hepatitis B virus during birth develop chronic hepatitis, an incurable disease that destroys the liver, Cohen said. Many of these children eventually need liver transplants. In rare cases, babies can die from overwhelming infections.

Why do newborns get the hepatitis B vaccine?

Doctors vaccinate babies on the first day of life because that’s when the vaccine is most effective, Dr. Ravi Jhaveri, head of infectious diseases at Lurie Children’s Hospital of Chicago.

When infants are infected during childbirth, the hepatitis B virus enters their bloodstream and heads for the liver, where it can set up a lifelong infection, Jhaveri said. Vaccinating newborns just after delivery gives their immune system the chance to fight off the infection quickly, rather than allowing the virus to multiply and gain a foothold. Studies show that vaccinating older babies exposed to hepatitis B isn’t effective, he said.

Hepatitis B spreads through contact with infected blood and bodily fluids — even microscopic amounts — and is incredibly infectious.

Children can be infected in the home by people with the virus, especially if they share toothbrushes, razors and earrings, Cohen said. Vaccinating newborns before they leave the hospital protects them from being infected throughout childhood.

Dr. Su Wang, an internal medicine doctor, learned she had hepatitis B after donating blood when she was in college. Although her mother did not have the disease, other family members did.

Wang takes antiviral medicine for hepatitis B and remains healthy. She said she made sure that all four of her children got the vaccine when they were born, along with a dose of hepatitis B immunoglobulin, which provides the body with extra antibodies. While vaccines can take a week or two to take full effect, immunoglobulin provides immediate protection from the virus, Wang said.

“It is such a relief that I don’t have to worry about my four kids having hepatitis,” Wang said.

When the hepatitis B vaccine was first introduced in 1982, doctors provided it only to adults at high risk. Two years later, the CDC recommended the vaccine for high-risk newborns, Jhaveri said. The number of perinatal infections stayed stubbornly high.

But hepatitis B infections plummeted after the CDC began recommending a universal dose of hepatitis B vaccine at birth in 1991. Cases of acute hepatitis B infections among children fell 99% from 1990 to 2019. Infection rates remained the same or increased among adults over 40 from 2010 to 2019.

Vaccinating babies appears to protect them for at least several decades, Jhaveri said.

Although people who inject drugs are at high risk for hepatitis B, doctors aren’t seeing many cases of the infection in people in their teens, 20s and 30s — the generations young enough to have been vaccinated at birth, Jhaveri said. As the generations of children vaccinated at birth get older, doctors will learn whether those shots prevent infections into middle age or longer.

“It’s really a horrible disease,” Dr. James Campbell, vice chair of the American Academy of Pediatrics’ Committee on Infectious Diseases. “For a very cheap vaccine that is known to be safe and effective, we can eliminate perinatal hepatitis B.”

If the CDC’s upcoming vaccine panel recommends against hepatitis B vaccination at birth, it could make the vaccine more difficult to get. CDC vaccine recommendations influence which immunizations are covered by insurance, and all CDC-recommended vaccines are included in the federal Vaccines for Children program, which makes immunizations available for free. About half of children in the United States are eligible for free vaccines through the program.

Last month, Kennedy had newly confirmed CDC Director Susan Monarez fired because, she said in a Wall Street Journal editorial, she wouldn’t “preapprove” the vaccine panel’s recommendations.

What to know about hepatitis B

When adults are infected with hepatitis B, their immune system often overcomes the virus, so that it’s no longer a threat, Campbell said. Babies, whose immune systems are undeveloped, typically develop chronic infection for the rest of their lives.

The longer that people live with the chronic inflammation caused by infection, the higher their risk of liver damage and cancer, Cohen said. No child should develop cancer from a preventable infection, she said.

“We want to give every baby born in the U.S. the absolute right to a long healthy life,” she said, “not an increased risk of cancer from the day they’re born.”

Cassidy, the Louisiana senator, has been a vocal supporter of the hepatitis B vaccine.

In his home state of Louisiana, he created a public-private partnership to vaccinate 36,000 children from the Baton Rouge area against hepatitis B at no cost.

During Kennedy’s confirmation hearing in January, Cassidy told a story about the “worst day of my medical career,” recounting his experience treating a young woman with hepatitis B on her way to a liver transplant. “That was an inflection point in my career,” he said. “Since then, I’ve tried to do everything I can to make sure I never have to speak to another parent about their child dying due to a vaccine-preventable disease.”

Preventing disease is virtually always cheaper than treating it. Hepatitis B shots are some of the least expensive vaccinations. A liver transplant in 2020 cost $878,400. Treating liver cancer costs $93,228, according to a 2024 study.

A 2015 study found that the United States spent more than $1 billion a year on hospitalizations for hepatitis B.

“There are people that are in their teens and their 20s that may die of liver cancer because of hepatitis B, when they would otherwise be healthy and thriving people,” Jhaveri said. “These are risks we’ll be taking on if we stopped using this safe and effective vaccine.”