Delaying the first hepatitis B shot until babies are 2 months old could increase chronic hepatitis B infections acquired by age 20 by about 19%, according to a computer model from researchers at Mass General Brigham in Boston. A shared decision-making approach, now part of federal guidance, was projected to raise infections by about 83%.
The findings, published in Annals of Internal Medicine on Oct. 19, are projections, not observed cases. They estimate what could happen to one year of U.S. births under different vaccine timing policies, not what has already happened.
