Long-term immunity to hepatitis B following vaccination in infancy: Real-world data analysis.

BACKGROUND: Hepatitis B virus (HBV) vaccination has decreased the prevalence of chronic HBV infections and their sequelae. However, whether vaccination at birth provides lifelong protection is unclear.

OBJECTIVE: To assess long-term immunity following neonatal HBV immunization in a large population-based cohort.

METHODS: Using the database of a 2 million member sick fund in Israel, we identified all subjects born after introduction of universal HBV vaccination in Israel (January 1992 through December 2014), that were tested for hepatitis B surface antibody (anti-HBs Ab's). Years since vaccination were categorized into 5-year groups and linear trends in the seroprevalence of HBV immunity were calculated. Anamnestic response and presence of Hepatitis B surface antigen (HBs Ag) were assessed.

RESULTS: Included were 20,634 tested individuals. Mean (±SD) age at testing was 14.8 (±5.4) years. Mean anti-HBs Ab levels declined with time to 16.39 mIU/ml in the 15-20 year group (P < 0.001). The proportion of negative results increased gradually (P < 0.001) to 66.7% after 15 years. Anamnestic response assessment showed that 604 of 644 seronegative subjects (93.8%, 95% CI: 91.6-95.5%) became seropositive after a booster dose. HBs Ag was identified in 91 of the 20,634 (4.4 per 1000 study participants).

CONCLUSIONS: Following vaccination, anti-HB's Ab's progressively decline, with only a third of the population retaining protective levels after 15 years. In adolescence, anamnestic response shows that nearly all revaccinated adolescents exhibit immunity. A low rate of Hepatitis B infection was demonstrated despite vaccination of nearly all newborns.