Incidence of hepatitis C virus infection in the prison setting: The SToP-C study

People in prison are at high risk of HCV given high injecting drug use prevalence. This study evaluated HCV incidence and associated injecting drug use characteristics in prison. The SToP-C study enrolled people incarcerated in four Australian prisons. Participants were tested for HCV at enrolment and then every 3-6 months (October-2014 to November-2019). Participants eligible for this analysis included those at-risk of HCV primary infection (anti-HCV negative) or re-infection (anti-HCV positive, HCV RNA negative) with follow-up assessment. A total of 1643 eligible participants were included in analyses (82% male; median age 33 years; 30% injected drugs in prison; 1818 person-years of follow-up). Overall HCV incidence was 6.11/100 person-years (95%CI: 5.07-7.35), with higher rate of re-infection (9.34/100 person-years; 95%CI: 7.15-12.19) than primary infection (4.60/100 person-years; 95%CI: 3.56-5.96). In total population (n = 1643), HCV risk was significantly higher among participants injecting drugs in prison [vs. no injecting; adjusted hazard ratio (aHR): 10.55, 95%CI: 5.88-18.92), and those who were released and re-incarcerated during follow-up (vs. remained incarcerated; aHR: 1.60, 95%CI: 1.03-2.49). Among participants who injected recently (during past month, n = 321), HCV risk was reduced among those receiving high-dosage opioid agonist therapy (OAT), i.e. methadone >= 60 mg/day or buprenorphine >= 16 mg/day, (vs. no OAT, aHR: 0.11, 95%CI: 0.02-0.80) and increased among those sharing needles/syringes without consistent use of disinfectant to clean injecting equipment (vs. no sharing, HR: 4.60, 95%CI: 1.35-15.66). This study demonstrated high HCV transmission risk in prison, particularly among people injecting drugs. High-dosage OAT was protective, but improved OAT coverage and needle/syringe programmes to reduce sharing injecting equipment are required.