title: Will Infant Hepatitis B Vaccination Protect Into Adulthood?: Extended Canadian Experience After a 2-, 4- and 6-month Immunization Schedule.
abstract: Hepatitis B virus (HBV) vaccination programs generally target infants to prevent chronic HBV infection and/or preadolescents to reduce transmission in adulthood. To assess whether infant HBV immunization can potentially accomplish both objectives, we measured residual immunity 10-16 years after vaccination in Canadian children.
  
  
  
  A prospective, parallel group, single center study enrolled adolescents given HBV vaccine at 2, 4 and 6 months of age. Exclusion criteria included prior HBV infection and additional vaccinations. At follow-up anti-HBs testing, participants were 10-11 or 15-16 years old; those with <12 mIU/mL anti-HBs by the assay used were challenged with HBV vaccine to assess immune memory-based responsiveness.
  
  
  
  A total of 137 tested participants were 10-11 and 213 were 15-16 years old, respectively; none had evidence of prior HBV infection. At baseline, 78% of younger and 64% of older participants had <12 mIU/mL anti-HBs (P = 0.006) and were challenged with vaccine: 103/106 (97.2%) younger and 123/135 (91.1%) older participants developed ≥12 mIU/mL anti-HBs (P = 0.06), with geometric mean antibody concentration of 590 (95% confidence interval: 473-737) and 319 mIU/mL (95% confidence interval: 229-445; P = 0.004), respectively. Immune memory loss may have occurred in 3 younger (2.2%) and 12 older children (5.6%; P = 0.06) who were nonresponsive to first but not second vaccine challenge.
  
  
  
  After HBV vaccination at 2, 4 and 6 months of age, most adolescents had little or no residual antibody but nearly all responded to HBV challenge, confirming immune memory persistence. However, anamnestic responses were weaker in 15- to 16-year olds and lost in some. Booster responses in 10- to 11-year olds were vigorous in comparison. Extended evaluation of protection is warranted.
authors.affiliation: From the *Vaccine Evaluation Center, Vancouver, British Columbia, Canada; †University of British Columbia, Vancouver, British Columbia, Canada; ‡Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada; and §BC Centre for Disease Control, Vancouver, British Columbia, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Pinto
authors.forename: Meena
authors.initials: M
authors.lastname: Dawar
authors.forename: Mel
authors.initials: M
authors.lastname: Krajden
authors.forename: Monika
authors.initials: M
authors.lastname: Naus
authors.forename: David W
authors.initials: DW
authors.lastname: Scheifele
mesh_terms: D000293:Adolescent; D002170:Canada; D002648:Child; D006509:Hepatitis B / Q000276:immunology* / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood* / Q000276:immunology; D017325:Hepatitis B Vaccines / Q000008:administration & dosage / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D011446:Prospective Studies
chemical_list: D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines