title: Opioid substitution therapy protects against hepatitis C virus acquisition in people who inject drugs: the HITS-c study.
abstract: OBJECTIVE
  To estimate hepatitis C virus (HCV) incidence and identify associated risk and protective factors among people who inject drugs (PWID) in Sydney, New South Wales.
  
  
  METHODS
  Community-based prospective observational study of serologically confirmed HCV antibody-negative PWID enrolled in six Sydney neighbourhoods located in three distinct regions between 10 November 2008 and 31 October 2011.
  
  
  METHODS
  Serologically confirmed HCV incidence per person-years (py); and self-reported demographic and behavioural risk factors for HCV infection.
  
  
  RESULTS
  The overall incidence of HCV infection was 7.9/100 py. Risk factors independently associated with incident HCV infection were younger age (adjusted hazard ratio [AHR] for age < 27 years, 5.66; 95% CI, 1.69-18.95; P = 0.005) and daily or more frequent injecting (AHR, 4.06; 95% CI, 1.15-14.30; P = 0.03). Opioid substitution therapy (OST) was protective against HCV seroconversion and was associated with a reduced risk of incident infection among those who mainly injected heroin or other opioids (AHR for those not receiving OST while mainly injecting heroin or other opioids, 5.64; 95% CI, 1.30-24.42; P = 0.02).
  
  
  CONCLUSIONS
  The observed HCV incidence was substantially lower than the incidence of 30.8/100 py observed a decade earlier in a similar NSW-based cohort, suggesting a decline in HCV incidence among PWID. This is likely due to increased coverage of OST, combined with a probable decrease in the population of PWID.
authors.affiliation: The Kirby Institute, University of New South Wales, Sydney, NSW, Australia. lmaher@kirby.unsw.edu.au.
authors.forename: Bethany
authors.initials: B
authors.lastname: White
authors.affiliation: The Kirby Institute, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Dore
authors.affiliation: Inflammation and Infection Research Centre, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Lloyd
authors.affiliation: Virology Division, SEALS Microbiology, Prince of Wales Hospital, Sydney, NSW, Australia.
authors.forename: William D
authors.initials: WD
authors.lastname: Rawlinson
authors.affiliation: The Kirby Institute, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Lisa
authors.initials: L
authors.lastname: Maher
mesh_terms: D000328:Adult; D006526:Hepatitis C / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D006801:Humans; D015994:Incidence; D058850:Opiate Substitution Treatment; D011446:Prospective Studies; D015819:Substance Abuse, Intravenous / Q000150:complications