Long-term immunogenicity of hepatitis B vaccination in a cohort of Italian healthy adolescents.

In 1992, 620 adolescents were vaccinated against hepatitis B. Anti-HBs concentrations were measured in 480 (77.4%) adolescents 1 month after completion of the primary course of vaccination. To assess the persistence of anti-HBs, 347 and 228 of such vaccinees were retested for anti-HBs in 1999 and for anti-HBs and anti-HBc in 2003. More than 10 years after vaccination, individuals with anti-HBs >or=10 mIU/ml were considered protected while those with antibody <10 mIU/ml were given a booster dose and retested 2 weeks later. Check performed in 2003 showed that 208/228 (91.2%) vaccinees retained protective concentrations of anti-HBs. All vaccinees were anti-HBc negative. 11 of the 12 (91.7%) individuals who were given a booster dose of vaccine showed a vigorous anamnestic response while the remaining one showed a weak response (10.6 mIU/ml). These data suggests that hepatitis B vaccination can confer long-term immunity and that immunological memory can outlast the loss of antibody. Hence, the use of routine booster doses of vaccine does not appear necessary to maintain long-term protection in successfully vaccinated immunocompetent individuals.