title: Impact of hepatitis B immunization among the Nicobarese tribe--antibody titres & seroprotection five years after vaccination.
abstract: OBJECTIVE
  A total of 237 Nicobarese subjects who had received hepatitis B vaccination as part of mass vaccination project during 2000-2001 were screened for anti-HBsAg titres by quantitative ELISA five years after vaccination.
  
  
  METHODS
  Anti-HBsAg antibody was estimated using quantitative ELISA. Proportion of the subjects with protective levels of antibody and geometric mean antibody titres were calculated.
  
  
  RESULTS
  Among the 237 study subjects, 213 had received three doses of vaccine, 17 had received two doses and seven had received one dose. The geometric mean titres of anti-HBs antibodies were 201.7, 31.9 and 23.1 mIU/ml among those who received three, two and one dose of vaccine, respectively. Among those who received three doses of vaccination, 85.9 per cent had anti-HBs antibody levels of 10 mIU/ml or more, indicating seroprotection. The difference in the seroprotection rates among those who received three doses of vaccination (85.9%) and those who received less than three doses (58.3%) was significant. Seroprotection rates one month after the first, second and third dose of vaccination were 49.1, 86.9 and 96.7 per cent, respectively. It then declined to 89 per cent by the end of the second year and to 85.5 per cent by the end of the third year, but there was no decline thereafter.
  
  
  CONCLUSIONS
  Seroprotection rate reached at the maximum one month after the third dose of HBV vaccine. Although about 15 per cent of the vaccinated persons lost seroprotection by the end of the third year, no further loss in seroprotection was observed between the third year and the fifth year.
authors.affiliation: Regional Medical Research Centre (ICMR), Port Blair, Andaman & Nicobar Islands, India.
authors.forename: A P
authors.initials: AP
authors.lastname: Sugunan
authors.forename: Haimanti
authors.initials: H
authors.lastname: Bhattacharya
authors.forename: Debdutta
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: A
authors.initials: A
authors.lastname: Mandal
authors.forename: S R
authors.initials: SR
authors.lastname: Ghosal
authors.forename: R C
authors.initials: RC
authors.lastname: Rao
authors.forename: A K
authors.initials: AK
authors.lastname: Mandal
mesh_terms: D000914:Antibodies, Viral / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005006:Ethnicity / Q000706:statistics & numerical data*; D006509:Hepatitis B / Q000453:epidemiology* / Q000276:immunology*; D006801:Humans; D007194:India / Q000453:epidemiology; D007195:Indian Ocean Islands / Q000453:epidemiology; D032541:Mass Vaccination / Q000706:statistics & numerical data*; D016036:Seroepidemiologic Studies; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000914:Antibodies, Viral