Ending the practice of immunising all newborns against hepatitis B, as Health Secretary Robert F. Kennedy Jr has recommended, would sharply increase the number of chronic infections and put more than half of Americans at risk of the disease by age 20, according to a new study published on Oct 20.
Hepatitis B is a highly contagious virus that can lead to cirrhosis, liver failure and liver cancer. To prevent infections, doctors in the United States have for decades administered the first dose of the hepatitis B vaccine to all babies within 24 hours of birth – and within 12 hours to infants whose mother is known to be infected.
But in December 2025, a panel of advisers chosen by Kennedy recommended that parents should decide whether, or when, infants should get the shot if they were born to mothers who test negative for hepatitis B. In those cases, the group said, parents should decide “no earlier than 2 months of age”.
Kennedy and his associates have argued that hepatitis B is primarily a sexually transmitted disease and that babies do not need the protection unless their mothers are infected. But the virus can be spread by people who do not know they have it, as well as by household objects used by an infected person.
In January, Kennedy proposed a new childhood vaccination schedule in which the vaccine would be offered under a shared clinical decision-making approach – that is, after consultation with a healthcare provider.
In March, a federal judge temporarily blocked the implementation of the December and January recommendations. But the lawsuit continues.
Amir Mohareb, an infectious diseases physician at Massachusetts General Hospital and Harvard Medical School who led the study, and his colleagues modelled the potential impact of changing hepatitis B vaccination policy on the estimated 3.6 million infants born in a single year.
Immunising babies at two months of age rather than at birth would increase chronic hepatitis B infections acquired by age 20 by 19%, from an average of 255 cases per year to 303, the study found.
Switching to a shared decision-making policy would increase chronic infections by 83%, to an average of 467 cases, and would result in more than 50% of children born each year entering adulthood susceptible to infection. The findings were published in the journal Annals of Internal Medicine.
The Department of Health and Human Services did not provide comment. NYTIMES
This article originally appeared in The New York Times.