Most new parents don't give much thought to the shots their baby gets in the hospital. The hepatitis B dose at birth has been a quiet part of the US newborn routine for more than three decades. That piece of ordinary care has been under debate for the past year.
A new modeling study from Harvard Medical School and Massachusetts General Hospital projects that proposed changes to that shot could sharply raise chronic childhood infections. It was published in the Annals of Internal Medicine in October 2026.
Depending on how many families still vaccinate, the model estimates an 83 to 225 percent rise in chronic childhood infections. A milder change that only delays the first dose to 2 months would still lift chronic infections by 19 percent by age 20.
What the researchers modeled
The team ran a computer simulation following 3.6 million US babies born in a single year all the way to age 20. They compared the current birth-dose schedule with two alternatives now on the policy table.
Also read: Heavy ultra-processed eaters had 40% higher odds of brain damage they can't feel yet
The first alternative postpones the first shot until 2 months of age. If 75 percent of families still get their baby vaccinated on time, chronic childhood infections rise by 19 percent.
The second alternative is called shared clinical decision-making, where parents and clinicians make the call together. In that version, chronic infections climb by at least 83 percent, depending on how many families follow through.
The 225 percent figure comes from the worst-case uptake. If only about one in four families take up vaccination under shared decision-making, chronic childhood infections more than triple compared with the current birth-dose plan.
The raw head count is just as stark. Under the current universal birth dose, around 232,000 of those 3.6 million children would still be susceptible to hepatitis B by age 20.
Also read: Hepatitis A and B: One causes more than 1 million deaths a year
Under shared decision-making, that number climbs to roughly 1.8 million.
Where the policy stands right now
The scenarios aren't theoretical. In December 2025, the CDC's advisory committee voted to end the universal birth-dose recommendation for babies whose mothers test negative for hepatitis B.
The agency moved to a shared clinical decision-making model in January 2026. NBC News reported that a federal judge in Massachusetts stayed those changes in March 2026, so the universal birth dose stays in place for now.
Lead author Dr. Amir Mohareb is an infectious disease physician at Massachusetts General Hospital. He told Mass General Brigham that "even under the most optimistic conditions, the new recommendations could increase childhood hepatitis B infections by more than 80%."
Also read: Explained: COVID-19
The CDC still lists the hepatitis B birth dose as part of the routine US newborn immunization schedule. The underlying court case brought by the American Academy of Pediatrics is still open.
Also read: Walk fewer than 5,000 steps a day? Your risk of dementia and stroke may nearly double
This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.