Study: Household Hepatitis B Exposure a Risk for Unvaccinated Children

Basing hepatitis B virus vaccination recommendations for infants solely on the birth mother 's HBV status leaves children vulnerable to infection from other close contacts , including household members who may carry the virus, according to new findings presented at ID Week 2026 . The study is the first of its kind examining sources of child household exposure to HBV.

The research included 158,000 children under age 5 in 131,000 households who lived with one or more Kaiser Permanente Northern California members on June 16, 2023. The study identified 2,024 children liv ing in a household with a person with active HBV , creating an opportunity for potential exposure . Among these children, 846 (41.8%) were exposed to HBV by their birth mother and 1,178 (58.2%) were potentially exposed by another household member with HBV . All children born to a mother with HBV were vaccinated within seven days of birth . In contrast, only 93.5% of children living with another household member with HBV were vaccinated .

In January 2025, t he U.S. Centers for Disease Control and Prevention changed its HBV vaccination guidance. Previously, the recommendation was for all infants to be vaccinated at birth. The new recommendation specifies vaccination should only be for infants whose mothers have unknown or active HBV status. However, HBV can be transmitted after birth through contact with body fluids including blood, tears and saliva. In addition, t he virus can live on environmental surfaces for up to a week. As a result, individuals who share a household with a person with active HBV are at high risk of infection , according to researchers .

Researchers say the new findings underscore the importance of universal hepatitis B vaccination at birth.

" A child can be exposed to hepatitis B from anyone with an active infection, not just their mother ," said Karen B. Jacobson, MD, MPH, infectious disease s physician and research scientist at the Vaccine Study Center at the Kaiser Permanente Division of Research. " No one know s the status of everyone a child may come into contact with , and vaccinating infants at birth protects against known and unknown potential sources of transmission. The hepatitis B vaccine is a safe and effective way to protect against HBV infection ."

CDC estimates approximately 640,000 U.S. adults live with chronic hepatitis B . When infected early in life, 90% of infants will develop chronic hepatitis B, which can cause lifelong complications including cirrhosis and liver cancer .

In addition to Dr. Jacobson , study co- authors include: Andrew Watson, MS, MA; Helena Archer, PhD , MPH; Sally Stephens, MPH; Lauren D. Liao, PhD; Ousseny Zerbo, PhD; and Nicola P. Klein, MD , PhD.

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About ID Week

ID Week is the joint annual meeting of the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, the HIV Medicine Association and the Pediatric Infectious Diseases Society. ID Week is a recognized forum for peer-reviewed presentations of new research on scientific advances and bench-to-bedside approaches in prevention, diagnosis, treatment and epidemiology of infectious diseases, including HIV, across the lifespan . For more information, visit idweek.org .