New longitudinal study suggests booster vaccination may not be necessary despite declining antibody levels.
Hepatitis B surface antigen and antibody testing
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A recent study published in npj Vaccines challenges the prevailing assumption that hepatitis B surface antibody (anti-HBs) levels below 10 mIU/mL signify loss of immunity in children vaccinated against hepatitis B virus (HBV). The research followed 395 children born to HBV-infected mothers over a 5.4-year period and found no cases of breakthrough HBV infection, even in those whose antibody levels fell below the traditional protective threshold.1
At the start of the study, about 27% of children had anti-HBs antibody levels below the 10 mIU/mL threshold, which increased to 42% at follow-up, approximately 5 years later. Despite this decline, none of the 395 children, including those unboosted with low antibody levels, developed hepatitis B infection or tested positive for hepatitis B surface antigen (HBsAg). Notably, 15% of unboosted children showed increased antibody levels over time without evidence of infection, suggesting natural immune boosting from HBV exposure in this high-risk group. These results indicate that children vaccinated against HBV remain protected even when their anti-HBs levels fall below the traditionally accepted protective threshold.1
Children vaccinated against hepatitis B remain protected despite anti-HBs levels dropping below 10 mIU/mL.
Booster vaccination may not be necessary even in children with close contact to HBV-infected mothers.
Natural immune boosting can occur in vaccinated children following HBV exposure without causing infection.
The cohort included children with close HBV exposure due to maternal infection, monitored twice, initially at a mean age of 3.2 years and again at 8.6 years. Participants were categorized based on whether they received a hepatitis B vaccine booster after the first measurement. Researchers assessed serological markers, including anti-HBs, HBsAg, and antibody to hepatitis B core antigen (anti-HBc).1
The study acknowledged a relatively small subset with low antibody levels, and booster decisions were parent- and physician-driven rather than randomized. Cellular immunity was not assessed, which could also contribute to long-term protection.1
Chronic HBV infection remains a global health concern, especially due to mother-to-child transmission (MTCT). Neonatal immunoprophylaxis, involving a hepatitis B vaccine series and immunoglobulin administration shortly after birth, is the standard preventive measure. Anti-HBs levels ≥10 mIU/mL are typically considered protective, but the clinical significance of antibody levels declining below this has been uncertain.2
These findings support the notion that declining anti-HBs levels below 10 mIU/mL do not necessarily indicate loss of immunity and that routine booster vaccination may not be required, even in high-risk populations. This could influence future hepatitis B vaccination guidelines and reduce unnecessary booster administration.
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