title: A nationwide survey of past hepatitis A infections among Canadian adults.
abstract: BACKGROUND
  Hepatitis A virus (HAV) infection rates in Canada are low and declining. A nationwide pediatric serosurvey in 2003 confirmed that HAV infection is uncommon in children. Additional seroepidemiological data for adults would help to guide domestic use of HAV vaccines.
  
  
  METHODS
  A country-wide survey of HAV antibody positivity and selected risk factors was conducted among 18-69 year olds identified by random digit dialing, in samples proportional to regional populations. Volunteers were sent study materials and returned oral fluid and completed questionnaires by mail. An ultra-sensitive assay was used to detect HAV antibody in oral fluid. Multiple logistic regression was used for risk factor assessment.
  
  
  RESULTS
  Of 2104 potential study participants, 1552 (74%) returned an adequate oral fluid specimen and questionnaire. Anti-HAV was detected in 509 individuals (33%) and was associated with birth in HAV endemic areas, self-reported hepatitis A vaccination, prior travel to endemic areas, and increasing age. Only 15% reported having been vaccinated. Among Canadian-born, non-vaccinated participants anti-HAV was present in 20%, ranging regionally from 14% to 30%. Age-specific positivity rates in this subset were: 18-29 years 2.6%; 30-39 years 6.1%; 40-49 years 11.4%; 50-59 years 26.4% and 60-69 years 45.9%. Travel to HAV-endemic countries was reported by 55% of participants but only 24% of travelers had been vaccinated.
  
  
  CONCLUSIONS
  Past HAV infection rates among Canadian-born, non-vaccinated individuals are low in young adults and increase by two-fold per age decade. Travel to endemic areas is a significant risk factor, amenable to prevention by greater use of HAV vaccine.
authors.affiliation: University of British Columbia, Vancouver, BC, Canada. dscheifele@cw.bc.ca
authors.forename: David W
authors.initials: DW
authors.lastname: Scheifele
authors.forename: Gaston
authors.initials: G
authors.lastname: De Serres
authors.forename: Vladimir
authors.initials: V
authors.lastname: Gilca
authors.forename: Bernard
authors.initials: B
authors.lastname: Duval
authors.forename: Ruth
authors.initials: R
authors.lastname: Milner
authors.forename: Margaret
authors.initials: M
authors.lastname: Ho
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Ochnio
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002170:Canada / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006506:Hepatitis A / Q000453:epidemiology*; D035922:Hepatitis A Antibodies / Q000032:analysis; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014195:Travel; D055815:Young Adult
chemical_list: D035922:Hepatitis A Antibodies