title: A double-dose hepatitis B vaccination schedule in travelers presenting for late consultation.
abstract: BACKGROUND
  Vaccination against hepatitis B virus (HBV) is recommended for all travelers visiting HBV-endemic countries. However, travelers often present with insufficient time for the standard HBV vaccine schedule (SVS). We examined seroprotection against HBV following an alternative two-visit vaccination schedule (TVS) with currently available vaccine products, and completion rates with this TVS.
  
  
  METHODS
  A retrospective cohort study was conducted in three travel clinics in British Columbia, Canada. Adults ≥20 years old traveling to an HBV-endemic country, and unable to complete the standard or rapid HBV vaccination schedule before departure, were offered a TVS that consisted of a double dose of HBV vaccine at day 0, followed by a single dose in 4 to 12 months. Immunity to HBV [anti-HBV surface antigen (HBs) ≥10 mIU/mL] was determined 1 to 6 months following the final dose of HBV vaccine. Logistic regression modeling was used to assess correlates of seroprotection. We also determined completion rate with this TVS at two clinics.
  
  
  RESULTS
  In total, 117 participants (age range, 21-81 years, median age 57) met the inclusion criteria. Of these, 97 (82.9%) were immune after the TVS. Immunity was demonstrated in 93.1% of patients <50 years old and 79.5% of patients ≥50 years old. Increasing age was associated with reduced odds of developing immunity to HBV using the TVS [adjusted odds ratio = 0.954, 95% confidence interval (CI): 0.904, 1.008]. The completion rate of the TVS was 32.6% over a 12-month period. Completion rates varied between clinics (23.5% vs 48.4%, p < 0.001), suggesting that clinic-specific follow-up policies were important.
  
  
  CONCLUSIONS
  Seroprotection with completion of this TVS was similar to or exceeded that published in the literature for the SVS by age. However, even with a TVS, completion rates were low, underscoring the importance of follow-up. Further research is needed to determine whether travelers are protected prior to completion of this TVS.
authors.affiliation: School of Population and Public Health, Vancouver, British Columbia, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.forename: Michael
authors.initials: M
authors.lastname: Payne
authors.forename: Susan
authors.initials: S
authors.lastname: Hollenberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001955:British Columbia / Q000453:epidemiology; D015331:Cohort Studies; D003140:Communicable Disease Control; D004306:Dose-Response Relationship, Immunologic; D004334:Drug Administration Schedule; D005260:Female; D006509:Hepatitis B / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood; D017325:Hepatitis B Vaccines / Q000008:administration & dosage* / Q000276:immunology; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D008297:Male; D008875:Middle Aged; D011322:Primary Prevention / Q000379:methods; D012044:Regression Analysis; D012189:Retrospective Studies; D014195:Travel; D014611:Vaccination; D055815:Young Adult
chemical_list: D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines