Background & Aims: Despite the success of a universal vaccination program against hepatitis B virus (HBV) in Taiwan, a small but substantial proportion of individuals remain infected by mutant viruses that escape the vaccine. We investigated the seroepidemiology and genotypic characteristic of HBV for long periods after neonatal vaccination. Methods: We measured hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc), and antibody to hepatitis B surface antigen (anti-HBs) in 1214 serum samples collected throughout Taiwan from individuals 0.6-87.8 years old in 2007. HBV DNA was detected using polymerase chain reaction and sequence analysis in vaccine recipients who tested positive for anti-HBc and/or HBsAg. Results: The overall seroprevalence of HBsAg and anti-HBc was significantly lower among individuals born after the initiation of the nationwide vaccination program (P <.001). However, we observed increasing seroprevalence of anti-HBc and isolated anti-HBs when subjects were grouped by age: at 10-14, 14-18, to 18-21 years of age, values were 0.4%, 1.9%, and 8.1% (P =.0135) and 43.7%, 55.4%, and 59.6% (P =.0093), respectively (χ 2 test for trend). A large increase was observed in the percentage of patients who tested positive for HBV DNA at 18-21 years of age (3.0% vs 0.2% [P =.002] for all eligible subjects and 5.7% vs 0.3% [P <.001] for subjects vaccinated with <3 doses). Five of 8 completely vaccinated individuals who were seropositive for HBV DNA carried variants with mutations in the S gene. Conclusions: Universal vaccination effectively controls HBV infection in children and adolescents. However, after adolescence, there is a significant increase in the seroprevalence of anti-HBs, anti-HBc, and HBV DNA, indicating that new preventative strategies are needed for adults.
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