Efficacy of Hepatitis B vaccine in those who lost Hepatitis B surface antigen during follow-up

Background: the level of hbsag in some chronic hepatitis b virus (hbv)-infected individuals may decline over time so that it is not detectable in serum.objective: to assess the efficacy of hbv vaccine in those who lost their hbsag without seroconverssionto anti-hbs antibody.patients and methods: from april 1993 to december 2008, of 1603 chronic hbv-infected individuals,34 (22 men and 12 women) became hbsag-negative in follow-up visits, with no detectable anti-hbs antibody and hbv dna in their sera. they received hbv vaccination at 0, 1 and 6 months (case group). fifty-two subjects (30 men and 22 women) who were negative for hbsag, anti-hbs and anti-hbc antibody, received hbv vaccination according to the said schedule (control group). anti-hbs antibody was assessed one month after the last dose of vaccination in the both groups.results: the mean±sd age of the case and control groups was 38±12.7 and 33.4±8.6 years, respectively(p=0.07). the sex distribution between these two groups were similar (p=0.652). the mean±sd years of follow-up for the case group was 7.6±4.5 years. anti-hbs antibody level ≥10 iu/l was found in 8 (24%) subjects in the case group and in 45 (87%) in the control group (p<0.001). the mean±sd anti-hbs antibody level in the case group was 68±32.66 and in the control group 344.6±38.9 iu/l (p<0.001).conclusions: we found that nearly 24% of chronic hbsag-positive subjects who lost their hbsagresponded to hbv and the remaining cases need to be followed for occult hbv infection.