Serum level of anti-hepatitis B surface antigen 6-8 years after hepatitis B vaccination at birth.

The duration of protection after hepatitis B vaccination in children is unknown. We determined the serum level of antibody to hepatitis B surface antigen (anti-HBsAg) in 273 randomly selected 7-9-year-old schoolchildren from Zanjan City, Islamic Republic of Iran, who had been fully vaccinated against hepatitis B starting at birth. Titres < or = 10 mlU/mL were considered unprotective. Just over half of the children (52%) had titres < or = 10 mlU/mL with no difference between the sexes, while 81 (29.7%) had no anti-HBsAg (0 mlU/mL). Three of the children had antibodies to hepatitis B core protein. More studies are needed to determine the necessity for or timing of booster doses.