Reinfection following direct-acting antiviral therapy for hepatitis C infection among people in prison with recent injecting drug use: the SHARP-P study

Background: Given sub-optimal harm reduction access, people in prison who inject drugs are at great risk of hepatitis C virus (HCV) infection, including reinfection following successful treatment. In New South Wales, Australia, prison-based opioid agonist treatment (OAT) is available, but there is no needle syringe programme. This study evaluated post-treatment HCV reinfection incidence among people in New South Wales prisons who inject drugs. Methods: SHARP-P was a cohort study of people with recent injecting drug use (previous six months) receiving direct-acting antiviral (DAA) treatment in New South Wales prisons (2019-21). Participants were recruited before commencing therapy and assessed every 3-6 months post-treatment for recurrent viremia. HCV genome sequencing and clinical follow-up data were used to classify recurrent viremia as: definite reinfection, possible reinfection, virological failure, and undefined. Person-time of observation was used to calculate reinfection incidence, overall and in sub-populations. Results: Of 201 participants, 154 (77%) with post-treatment follow-up were included in the analyses (median age 32 years, 20% women, 16% receiving OAT, 62% reported injecting drugs in the month before enrolment, of whom 95% shared injecting equipment in prison). Twenty-six episodes of recurrent viremia were detected, including 16 definite reinfections, three possible reinfections, one virological failure, and six undefined. During 103 person-years of follow-up, incidence of definite HCV reinfection was 15.5/100 person-years (95%CI, 9.525.3) overall, 19.4/100 person-years (95%CI, 11.2-33.4) among those injecting during follow-up, and 57.9/100 person-years (95%CI, 32.9-101.9) among those sharing injecting equipment. Conclusions: The high HCV reinfection incidence in prisons emphasises the need to enhance prison-based harm reduction measures including access to sterile injecting equipment, currently prohibited in Australian prisons. The finding that reinfection accounts for most recurrent viremia could assist retreatment clinical decision-making in prison.