title: Immunity to hepatitis B in two birth cohorts given plasma-derived or yeast-derived vaccine.
abstract: OBJECTIVE
  To determine the antibody response to either yeast-derived or low-dose, plasma-derived hepatitis B vaccine, in two cohorts of infants monitored by an immunisation coordinator and immunised by general practitioners.
  
  
  METHODS
  Infants born to two cohorts of non-carrier mothers in Northland were followed up, the first receiving a low-dose, plasma-derived vaccine, the second a yeast-derived vaccine. An immunisation coordinator enrolled the mothers into the programme during pregnancy, promoted full immunisation against hepatitis B and later obtained blood samples from their babies. In each cohort, four subsamples of babies, randomly assigned, were bled for estimation of antibody levels to hepatitis B at ages 18, 30, 42 and 54 months (1 1/2, 2 1/2, 3 1/2, 4 1/2 years). No infant was bled more than once.
  
  
  RESULTS
  In both cohorts, antibody levels declined significantly with age. By age 4 1/2 years, 5.1% of children (95% confidence interval (CI): 3.5-7.1) immunised with yeast-derived vaccine were estimated to have antibody levels to hepatitis B below the acceptable level for protection of 10 IU/L. The proportion for those immunised with plasma-derived vaccine was 14.3% (95% CI: 7.4-24.1).
  
  
  CONCLUSIONS
  Children receiving yeast-derived vaccine do not require a second booster dose at school entry, although this might be considered at age 11. There are grounds to suggest that those who received low-dose, plasma-derived vaccine (prior to 1990) should be offered a booster before age 11.
authors.affiliation: Department of Public Health, Wellington School of Medicine. salmond@wnmeds.ac.nz
authors.forename: C E
authors.initials: CE
authors.lastname: Salmond
authors.forename: D R
authors.initials: DR
authors.lastname: Bandaranayake
authors.forename: M
authors.initials: M
authors.lastname: Tobias
mesh_terms: D000375:Aging / Q000276:immunology; D000914:Antibodies, Viral / Q000097:blood*; D015331:Cohort Studies; D006509:Hepatitis B / Q000276:immunology* / Q000517:prevention & control*; D017325:Hepatitis B Vaccines / Q000276:immunology*; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D007117:Immunization, Secondary; D007231:Infant, Newborn; D010949:Plasma; D015003:Yeasts
chemical_list: D000914:Antibodies, Viral; D017325:Hepatitis B Vaccines