Changes to hepatitis B immunization schedule would increase infections, model predicts

Chronic hepatitis B virus (HBV) infections can cause life-threatening liver disease. Before December 2025, the Centers for Disease Control recommended universal vaccination at birth. In December 2025, the Advisory Committee on Immunization Practices (ACIP) recommended deferred vaccination when infants born of mothers without HBV are at least two months old. In January 2026, the CDC switched to recommending a “shared clinical decision-making” approach for infants born of mothers without HBV. Though these recommendations have been challenged by professional medical societies and public health agencies, their clinical impact on HBV is unclear.

In a new study, Mass General Brigham researchers used a model to simulate the impact of the new HBV vaccination recommendations on HBV infections and susceptibility. Compared with universal vaccination at birth, they estimated that delaying HBV vaccination until infants are two months old would increase the number of chronic HBV infections by around 19%, whereas a shared decision-making strategy would increase infections by around 83%. The results are published in Annals of Internal Medicine.

“We found that, even under the most optimistic conditions, the new recommendations could increase childhood hepatitis B infections by more than 80% and would result in more than half of children being susceptible to hepatitis B infection as they enter adulthood," said corresponding author Amir Mohareb, MD, an infectious disease physician and clinician researcher at the Center for Global Health at Mass General Brigham. "These findings show why policy makers should re-implement recommendations for universal hepatitis B vaccination at birth.”

To estimate the effects of different vaccination strategies, the researchers used a Markov cohort state-transition model that simulates the average life experiences and health outcomes for people over time. The model was built using published epidemiologic data and was validated by comparing its projections with real-world CDC estimates of pediatric hepatitis B infections.

Using the model, they followed 3.6 million people (one year’s worth of births in the U.S.) over the first 20 years of life, modeling a "shared decision making" scenario in which 50% of infants were vaccinated when they were 2 months old or older. In all scenarios, HBV vaccination was recommended for all infants whose mothers were known to be HBV-positive.

The researchers estimated that delayed HBV vaccination would increase the number of chronic HBV infections by around 19%, and the shared decision-making approach would increase infections by about 83% (255 individuals with chronic HBV versus 303 and 467, respectively).

The 2025 and 2026 recommended strategies would also increase the number of adults susceptible to HBV: under the universal vaccination at birth strategy, 232,000 people in the birth cohort would still be susceptible to HBV at age 20, compared with roughly 474,000 with delayed vaccination and 1.8 million with shared decision-making.

This increase in adult susceptibility is significant because HBV infections acquired in adulthood have a higher likelihood of leading to life-threatening conditions including acute liver failure. HBV is also a common cause of liver cancer. The number of HBV infections acquired during adulthood is also increasing in many parts of the U.S., in part due to injection drug use.

"Even a small increase in childhood HBV infections could have large clinical, public health, and economic effects," said Mohareb.

Authorship: In addition to Amir Mohareb, Mass General Brigham authors include Lakshmi Ganapathi, Caitlin Dugdale, Ruma Rajbhandari, Andrea Ciaranello, Anne Neilan, Arthur Kim and Emily Hyle. Additional authors include Ravi Jhaveri.

Disclosures: Disclosure forms are available with the article online.

Funding: This study was funded in part by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health (K01AI166126), the James and Audrey Foster MGH Research Scholar Award, and the Harvard University Center for AIDS Research (National Institute of Health grant P30 AI060354).

Paper cited: Mohareb, A et al. “Projected Effect of 2026 Federal Changes to the Childhood Immunization Schedule on Chronic Hepatitis B Virus Infections in the United States” Annals of Internal Medicine DOI: 10.7326/ANNALS-26-02135 

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