Modelling suggests replacing routine newborn vaccination with clinician-led decisions could sharply increase childhood infections and leave more people unprotected by age 20.
A recent computer model suggests that changes to federal hepatitis B vaccination guidance could substantially increase the number of children who remain unprotected against the virus, with as many as 1.8 million young adults still vulnerable by age 20 if routine newborn vaccination is replaced by a “shared clinical decision-making” approach. The study, published in the Annals of Internal Medicine and led by researchers at Mass General Brigham, comes as the long-running debate over infant hepatitis B shots has intensified after the CDC changed its recommendations in December 2025 and then saw those changes placed on hold amid legal challenges.
The CDC said in its December update that parents of babies born to mothers who test negative for hepatitis B could decide with a clinician whether to give the first dose at birth or wait until later, while infants born to mothers who test positive or whose status is unknown should still receive the vaccine within 12 hours. Yet the agency’s hepatitis B pages continue to state that all infants should receive vaccination, reflecting the unsettled status of the policy and the wider uncertainty now surrounding the schedule.
In the Mass General Brigham modelling exercise, researchers followed a hypothetical group of 3.6 million babies born in the United States in 2026 through their first 20 years. They compared three approaches: universal vaccination shortly after birth, delaying the first dose until at least two months of age, and leaving the timing to discussions between parents and clinicians. The analysis estimated that postponing vaccination to two months could raise chronic infections by 19%, while the shared decision-making option could lift infections by 83% versus routine newborn vaccination. It also projected that the number of children still susceptible at age 20 would rise from about 232,000 under universal birth dosing to 474,000 with delay, and to 1.8 million under the shared-decision model.
Physicians and public health specialists say the stakes are high because hepatitis B can be transmitted through blood and other bodily fluids, can go unnoticed for years, and may progress to serious liver disease, including cancer. The American Academy of Pediatrics still recommends a first dose within 24 hours of birth, and CDC guidance for prevention and vaccine administration continues to emphasise the importance of immunising infants, unvaccinated children and other at-risk groups. Dr Amir Mohareb, the study’s corresponding author, said the findings show why policymakers should restore universal newborn vaccination, while other clinicians warned that even modest confusion over whether the shot is optional could leave more families missing the early dose and more children falling behind on the full series.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
