ANTIBODY RESPONSE TO RECOMBINANT HEPATITIS B SURFACE ANTIGEN IN HEALTHY ADULTS FOLLOWING PRIMARY an‎d SUPPLEMENTARY VACCINATION

Background: A proportion of healthy adults and neonates do not respond to vaccination with hepatitis B surface antigen (HBsAg ). Re-vaccination induces a protective antibody response in a minor proportion of non-responders. Objective: To study the immunogenicity of primary and secondary vaccinations with recombinant hepatitis B vaccine in healthy adults, and to compare the results with those who obtained the vaccine only in the neonatal period. Methods: Ninety-one healthy adults were immunized with triple doses of recombinant hepatitis B vaccine given at 0, 1 and 6 months intervals. The responder individuals were arbitrarily classified into low and high responders, based on the anti-HBs antibody titer. The non-responder subjects were subsequently re-vaccinated with 2-5 additional doses of the vaccine. Anti-HBs antibody and HBs antigen were detected by a sandwich ELISA, and anti-HBc antibody was detected by a competitive ELISA. Results: A protective level of anti-HBs antibody (> 10 lU/L) was developed in 93.4% (85/91) of the vaccinees following primary vaccination. Only one of the non-responders (16.6%) seroconverted and developed low titer of anit-HBs antibody after administration of additional 3-5 vaccine doses. Conclusion: Our results suggest that unresponsiveness to hepatitis B virus (HBV) may be differentially regulated in adults as compared to neonates.