Title: Reinfection with hepatitis C virus following sustained virological response in injection drug users Running title: HCV reinfection following SVR in IDUs

242 words) Despite that 60-90% of injection drug users (IDUs) are infected with hepatitis C virus (HCV) infection, IDUs are often denied therapy based on concerns of reinfection following treatment. However, there are little data in this regard. We evaluated HCV re-infection following sustained virologic response (SVR) among HCV-infected IDUs having received HCV treatment in a multidisciplinary program. Following treatment, participants were encouraged to return at follow-up intervals of 1 year and illicit drug use histories were obtained. In those with SVR, HCV RNA testing by PCR was performed to determine if relapse or reinfection occurred. Among 58 receiving HCV treatment between January 2002 and December 2006, 60% (35 of 58) achieved an SVR. Patients were followed for a median of 2.0 years following SVR (range, 0.45.0 years), with ongoing illicit and injection drug use reported in 54% (19 of 35) and 46% (16 of 35). Of the 35 with SVR, 28 remained HCV RNA negative during follow-up (80%), with four lost to follow-up and one dying of hepatocellular carcinoma and two cases of reinfection were observed (2 of 35). The rates of reinfection were 3.2 per 100 p-y (95% CI:0.4, 11.5) overall and 5.3 per 100 p-y (95% CI:0.6, 19.0) among those reporting injecting following SVR (n=16). One of two participants with HCV re-infection spontaneously cleared virus following reinfection. In conclusion, the rate of reinfection following treatment for HCV infection among current and former IDUs engaged in a multidisciplinary program is low.