Persistence of antibody to hepatitis B surface antigen among vaccinated children in a low hepatitis B virus endemic area
A potential problem of hepatitis B immunization is that vaccine-induced antibody to hepatitis B surface antigen (anti-HBs) declines to low levels with age. This study investigated the persistence of anti-HBs in vaccinated children in a low hepatitis B virus (HBV) endemic area. Plasma samples of 938 children between ages of 8 months and 15 years were tested for the presence of anti-HBs. The seroprotection rate was 60%. Protective antibody level was detected in 65% of children one year after vaccination, and in 30%, 29% and 24% 5, 10 and 15 years after vaccination, respectively. The mean anti-HBs titer declined with post-vaccination time (to 66 mIU/mL in 1 year, 60 mIU/mL in 5 years, 40 mIU/mL in 10 years to 37 mIU/mL in 15 years after vaccination). Children vaccinated against HBV during infancy may show low levels of antibody during adolescence. Our data suggest that a booster dose of vaccine may be required in low HBV endemic areas.