RESPONSE TO AN EXTRA DOSE OF HEPATITIS-B VACCINE AND SPECIFIC ANTIBODY PERSISTENCE IN NONRESPONDERS TO PRIMARY IMMUNIZATION

Background: In a campaign to vaccinate health care workers, a three-do se schedule (0, 1, and 6 months) and a four-dose schedule (0, 1, 2, an d 14 months) with hepatitis B (HB) Vaccine were used. After primary im munization 26 subjects vaccinated with the 3-dose schedule and 4 subje cts vaccinated with the 4-dose schedule had undetectable anti-HBs titr es. Methods: All these 30 non-responders received an extra dose of the same vaccine 2 months after primary immunization and a booster dose w ith a yeast-derived Vaccine 6 years later. Anti-HBs levels were evalua ted 1 month after the extra dose and after the booster dose. Results: One month after the extra dose 26.9% (7 of 26) of the subjects vaccina ted with the 3-dose schedule became positive for anti-HBs. Six years l ater only two of these subjects had detectable anti-HBs. After the boo ster dose the seven subjects who responded to the extra dose showed an anamnestic type of response, and five additional subjects became posi tive for anti-HBs. Responders to the extra dose were significantly you nger than the non-responders. In the four-dose group only one subject responded to the extra dose, and that subject maintained protective an ti-HBs. Conclusion: About 25% of non-responders to primary HB Vaccinat ion could benefit from an extra dose, and these subjects show an anamn estic type of response to HBs antigen even after 6 years. This respons e seems to be influenced by age.