New study projects hepatitis B surge if Kennedy-era vaccine policy takes effect

A new modeling study published this week projects that a Trump administration policy change narrowing the recommendation for the newborn hepatitis B vaccine could, if it takes full effect, substantially increase the number of children who develop chronic hepatitis B infection — a lifelong condition that carries a meaningfully elevated risk of liver cancer and cirrhosis.

The study, published October 20 in Annals of Internal Medicine and led by infectious-disease researcher Amir Mohareb of Massachusetts General Hospital and Harvard Medical School, used computer simulation to model the hepatitis B status of a single year's cohort of roughly 3.6 million infants born in the United States, tracking outcomes over their first twenty years of life under different vaccination scenarios.

The findings vary widely depending on how parents and clinicians actually behave once given a choice, which is the point of the exercise. Under a scenario in which only about 26 percent of eligible infants are vaccinated at or near birth — the researchers' estimate of what might happen under "shared decision-making" — the model projects a 225 percent increase in chronic hepatitis B cases compared with universal vaccination at birth. Under a milder scenario, in which the first dose is simply delayed to two months of age but still reaches 75 percent of infants, chronic infections rise by about 19 percent.

The policy behind the numbers

The study is a response to a decision made nearly a year ago. On December 5, 2025, the CDC's Advisory Committee on Immunization Practices voted 8 to 3 to drop the longstanding universal recommendation that all newborns receive a hepatitis B vaccine dose within 24 hours of birth. In its place, the panel recommended "individual-based decision making" between parents and clinicians for infants born to mothers who test negative for the virus — the vast majority of US births — with the first dose, if delayed, given no earlier than two months of age, according to the Department of Health and Human Services. Infants born to mothers who test positive, or whose status is unknown, are still supposed to receive the vaccine and hepatitis B immune globulin within 12 hours of birth.

The CDC adopted the change on December 16, 2025, citing the reliability of prenatal screening and the low rate of perinatal transmission in the United States. HHS followed with a revised childhood immunization schedule on January 5, 2026.

The change did not survive long as official practice. On March 16, 2026, Judge Brian Murphy of the US District Court for the District of Massachusetts issued a preliminary injunction in a lawsuit brought by medical societies including the American Academy of Pediatrics and the American College of Physicians. The court found that Health Secretary Robert F. Kennedy Jr.'s appointments to the vaccine advisory panel had likely violated federal law governing advisory committees, and it stayed both those appointments and every vote the reconstituted panel had taken — including the hepatitis B birth-dose downgrade, according to the American College of Physicians. The universal birth-dose recommendation has been the official federal policy ever since, while the Justice Department appeals the ruling to the First Circuit.

What the earlier evidence showed

The new Annals paper builds on an earlier modeling study published in JAMA Pediatrics in late April 2026, which simulated a comparably sized US birth cohort and likewise concluded that replacing universal birth-dose vaccination with a targeted recommendation would probably increase neonatal infections, projecting hundreds of additional chronic cases annually even under optimistic assumptions about uptake. Both papers lean on a grim biological fact: up to 90 percent of infants infected with hepatitis B in their first year of life go on to develop chronic infection, which untreated carries roughly a one-in-four lifetime risk of death from liver cancer or cirrhosis. Universal birth-dose vaccination, in place since 1991, is credited with cutting pediatric hepatitis B infections in the United States by about 99 percent.

Confusion in the exam room

Because the injunction is preliminary and the appeal is unresolved, pediatricians, parents and state health officials are currently operating under three overlapping sets of signals: the pre-injunction universal recommendation that courts have restored as the law of the land, the narrower guidance HHS and Kennedy have said they still intend to pursue, and the American Academy of Pediatrics' own continued recommendation of a universal birth dose regardless of how the litigation resolves. Several Democratic-led states, including New York, Massachusetts, Rhode Island and Maine, have said they will keep directing clinicians toward universal vaccination no matter what happens in court.

"Parents are confused, given the recommendations from CDC, HHS, and Kennedy differ from established" guidance, Graham Tse, a pediatrician and chief medical officer at MemorialCare Miller Children's & Women's Hospital, told Healthline, adding that he sees "no argument whatsoever for changing the established vaccination schedule for hepatitis B."

That confusion matters beyond paperwork. Public-health researchers who have studied vaccine policy changes note that clinical practice often drifts toward new "optional" guidance well before litigation is resolved, simply because some providers and parents treat a change in federal messaging as license to delay — which is precisely the behavioral assumption driving the higher-end projections in both the Annals and JAMA Pediatrics models.

Who is affected, and what comes next

The roughly 3.6 million infants born in the United States each year are the direct subject of the dispute, though the practical effect for any individual family depends heavily on where they live, which hospital system delivers their care and how that system has chosen to interpret shifting federal guidance during the injunction period. Infants born to mothers who test positive for hepatitis B are not affected by any version of the policy change; they are still supposed to receive the birth dose under every scenario in play.

The First Circuit appeal, docketed as AAP et al. v. Kennedy et al., has no scheduled resolution date. Until it is decided, universal birth-dose vaccination remains the technically operative federal recommendation, insurers have told reporters that coverage for the birth dose is not changing, and the new modeling studies are likely to become part of the evidentiary record cited by medical societies as the case proceeds. Whether the appeals court sides with the administration or the plaintiffs will determine whether the scenario modeled in this week's study — lower birth-dose uptake driven by shared decision-making — becomes the operating reality for the next cohort of American newborns, or remains a hypothetical built into a simulation.