In persons receiving opioid agonist therapy, reinfection with Hepatitis C virus was low, although it was greatest among people who share needles and continued to inject drugs, and in the first 24 weeks post-treatment.

A 3-year cohort study aimed to examine the frequency of Hepatitis C virus (HCV) reinfection among patients receiving opioid agonist therapy (OAT) three years following successful treatment.

Among 296 chronic HCV-infected patients with genotypes 1, 4, or 6 and who were receiving stable OAT, 199 were included in the long-term extension study (CO-STAR - Hepatitis C Patients on Opioid Substitution Therapy Antiviral Response) and 286 were evaluable for reinfection. Reinfection with HCV was evaluated in serum samples. Drug testing of the urine was done.

Notably, 604 person-years of follow-up revealed a 1.7 per 100 person-year reinfection rate for HCV. Recent users of injectable drugs (1.9 per 100 person-years; 212 person-years) had a greater risk of reinfection. At the 6-month follow-up visit, 59% and 21% of subjects, indicated ongoing drug use and injecting drug use, respectively, which remained steady throughout the subsequent three years of follow-up.

Following treatment of HCV infection in individuals receiving OAT, the risk of HCV reinfection was low. However, reinfection rates were highest in the first 24 weeks following the completion of therapy and among subjects who continued to inject drugs and share syringes.