OUP accepted manuscript

Injection drug use (IDU) following treatment for hepatitis C virus (HCV) may lead to reinfection, particularly if access to harm reduction services is suboptimal. This study assessed HCV reinfection risk following direct-acting antiviral therapy within Australian prisons that had opioid agonist therapy (OAT) programs but did not have needle and syringe programs (NSP).The Surveillance and Treatment of Prisoners with hepatitis C (SToP-C) study enrolled people incarcerated in four prisons between 2014-2019. Participants treated for HCV were followed every 3-6 months to identify reinfection (confirmed by sequencing). Reinfection incidence and associated factors were evaluated.Among 388 participants receiving treatment, 161 had available post-treatment follow-up and were included in analysis (92% male; median age 33 years; 67% IDU in prison; median follow-up 9 months). Among those with recent (in the past month) IDU (n=71), 90% had receptive needle/syringe sharing. During 145 person-years (PY) of follow-up, 18 cases of reinfection were identified. Reinfection incidence was 12.5/100 PY (95%CI: 7.9-19.8) overall, increasing to 28.7/100 PY; (95%CI 16.3-50.6) among those with recent IDU and needle/syringe sharing. In adjusted analysis, recent IDU with needle/syringe sharing was associated with increased reinfection risk (adjusted hazard ratio [AHR] 14.62; 95%CI 1.84-116.28; p=0.011) and longer HCV testing interval with decreased risk (i.e., chance of detection; AHR 0.41 per each month increase; 95%CI 0.26-0.64; p<0.001).A high rate of HCV reinfection was observed within prison. Post-treatment surveillance and retreatment are essential to limit the impact of reinfection. High-coverage OAT and NSP should be considered within prisons.