Mass General Brigham researchers project 83% more childhood chronic hepatitis B if the CDC's optional birth dose, blocked by a court since March, takes effect

A Mass General Brigham model in Annals of Internal Medicine followed one year of U.S. births (3.6 million) for 20 years. Against 255 chronic hepatitis B infections with a universal birth dose, it projects 303 (19% more) if the first shot waits until two months, and 467 (83% more) under the CDC's January 2026 "shared decision-making" recommendation for babies of mothers who test negative, assuming half get vaccinated at two months or later. That recommendation is not in force: a federal judge stayed it on March 16, 2026, restoring the universal birth dose. The real number. That is 212 more chronic infections per year of births, an increase the authors call "modest, at least in the early years." The larger gap is protection: 1.8 million 20-year-olds still susceptible under shared decision-making, against 232,000 with a birth dose. Lower uptake. At 75% uptake of a delayed shot, the model projects 357 cases (40% more); at 26%, 575 (125% more), per MedPage Today. TIME reported these as 19% and 225%; 575 is 225% *of* 255. What next. A federal appeals court heard the administration's bid to lift the stay on Oct. 6, per The Hill; 15 states have also sued over the schedule changes.

What a negative maternal test still leaves, per a 10,003-child review:

• Unvaccinated children of negative-testing mothers: 6.16% infected in childhood
• Vaccinated starting at 6–8 weeks: 0.21%
• Vaccinated starting at birth: 0.05% (gap not statistically significant; sub-Saharan Africa data, not a U.S. estimate)