Kaiser Permanente study shows relying solely on the birth mother’s hepatitis B status leaves children vulnerable to infection from other close contacts
Basing hepatitis B virus (HBV) 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, a new Kaiser Permanente study found.
The research, presented at IDWeek 2026, is the first of its kind examining sources of child household exposure to the hepatitis B virus.
“A child can be exposed to hepatitis B from anyone with an active infection, not just their mother,” said Karen B. Jacobson, MD, MPH, an infectious disease physician and research scientist at the Vaccine Study Center at the Kaiser Permanente Division of Research. “No one knows 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.”
The study 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. Within this group, there were 2,024 children identified as living in a household with a person with active HBV, creating an opportunity for potential exposure.
Our findings underscore the importance of universal hepatitis B vaccination at birth.
— Karen Jacobson, MD, MPH
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 7 days of birth. In contrast, only 93.5% of children living with another household member with HBV were vaccinated.
In January 2025, the U.S. Centers for Disease Control and Prevention (CDC) 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, the 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.
“Our findings underscore the importance of universal hepatitis B vaccination at birth,” said Jacobson.
There are approximately 640,000 adults in the U.S. living 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.
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, of the Division of Research.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. KPDOR seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 720-plus staff, including 73 research and staff scientists, are working on nearly 630 epidemiological and health services research projects. For more information, visit divisionofresearch.kp.org.
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