A retrospective cohort study found that exposure to hepatitis B virus (HBV) in young children often came from someone other than their mother in the household. Among over 158,000 children younger than 5 years, 1.3% lived in a household with a person with active HBV infection.
According to the study, 58.2% of those children were exposed via contacts who were not their mothers, while 41.8% were exposed via their mothers. Karen Jacobson, MD, MPH, of the Kaiser Permanente Vaccine Study Center, presented the findings at the IDWeek annual meeting.
Jacobson noted that even if every maternal infection could be identified, this would not account for potential exposure to an infected father, grandparent, or another person living in the household. She also pointed out that anyone the children came into close contact with outside the household could pose a risk.
Transmission of Hepatitis B
Dr. Jacobson explained that nonmaternal transmission of hepatitis B to children is uncommon in the U.S. today, thanks to widespread vaccination programs. However, if immunization coverage declines, more newborns could face heightened exposure risks. A single vaccine dose given at birth helps shield infants from potential household-related HBV cases.
The CDC’s Advisory Committee on Immunization Practices (ACIP) has reversed its long-standing policy, no longer urging a standard hepatitis B vaccine dose at birth for infants whose mothers test negative for the virus. Instead, the committee now advocates for joint decision-making regarding vaccination when maternal infection is ruled out.
One analysis projected that the new shared-decision approach might raise chronic HBV cases by 83% over time.
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Vaccination Rates
Jacobson’s study showed that 4.2% of children exposed to HBV by a nonmaternal household contact were unvaccinated by age 30 days. This is within the 2-month window recommended by ACIP for delaying the first dose of the three-dose series.
While 95% of birth-exposed infants were tested for HBV, only 3.6% of children with household exposures were tested. All birth-exposed children were vaccinated within 7 days of birth. Children with household exposure were more likely to be vaccinated than those who weren’t exposed.
Jacobson and her team analyzed laboratory and vaccination data for children younger than 5 years who were members of Kaiser Permanente Northern California. The study found that nonmaternal household contacts were older and more likely to be male than maternal contacts.
Study Limitations
Jacobson acknowledged the study’s 1.3% household exposure figure may be too low, as HBV screening in children is not standard practice. The research also faced challenges, including possible address errors and undercounts if infected household members were not Kaiser Permanente patients.
Since HBV testing in children is irregular, Jacobson’s team could not confirm whether any household-exposed children contracted the virus. Yet, when infection occurs in early childhood, it almost always progresses to chronic illness with lasting health consequences.