Opioid substitution therapy protects against hepatitis C virus acquisition in people who inject drugs: The HITS-c study

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. Design, setting and participants: Community-based prospective observational study of serologically confi rmed HCV antibody-negative PWID enrolled in six Sydney neighbourhoods located in three distinct regions between 10 November 2008 and 31 October 2011. Main outcome measures: Serologically confi rmed HCV incidence per personyears (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). Conclusion: 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