PERSISTENCE OF ANTI-HBs ANTIBODY AND IMMUNOLOGICAL MEMORY IN CHILDREN VACCINATED WITH HEPATITIS B VACCINE AT BIRTH
AbstractAims: Vaccination with the hepatitis B surface antigen (HBsAg) induces protective levels ofantibody (anti-HBs = 10 IU/L) in majority of vaccinees. It has been shown that the levels ofanti-HBs antibody do wane after vaccination. The aim of this study was to evaluate thepersistence of anti-HBs antibodies in healthy Iranian children at 10 years after primaryvaccination and the response to a booster dose using recombinant hepatitis B vaccine. Materialsand Methods: Blood samples were collected from 146 healthy 10-11 years old children whoreceived primary course of Hepatitis B vaccine at 0, 1.5 and 9 months of age. The sera weretested for anti-HBs, antibody to Hepatitis B core antigen (anti-HBc) and HBsAg by ELISAtechnique. A single booster dose of recombinant hepatitis B vaccine was administeredintramuscularly to a total of 94 children, whose anti-HBs antibody was less than 50 IU/L (70children with anti-HBs <10 IU/L and 24 subjects with anti-HBs 10-50 IU/L). The sera ofchildren were re-tested for anti-HBs antibody levels at 4 weeks after booster vaccination.Results: At 10 years after primary vaccination 70/146 (47.9%) of children had protective levelsof antibody with geometric mean titer (GMT) of 68.12 IU/ml. All children were negative forHBsAg, although anti-HBc antibody was positive in 11 (7.5%) of children. In the 94 subjectswho received the booster dose the seroprotection and the GMT of anti-HBs antibody were25.5% and 9.58 IU/L at pre-booster time and rose to 95.75% and 575.6 IU/L after the boostervaccination, respectively. Seroprotection rates and mean titer of antibody similarly expressed inmales and females. Conclusion: The results of present study showed that at 10 years afterprimary vaccination with recombinant HB vaccine, 47.9% of the children had protective levelsof anti-HBs antibody. Moreover we have demonstrated an anamnestic response to boostervaccination that confirms the persistence of an effective immunological memory in vaccinees.Key words : Children, Hepatitis B vaccine, Anti-HBs antibody, Immunologic memory, Boostervaccination.
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