Modeling the role of incarceration in HCV transmission and prevention amongst people who inject drugs in rural Kentucky

Background: People who inject drugs (PWID) experience high incarceration rates, with current/recent incarceration being associated with increased hepatitis C virus (HCV) transmission. We assess the contribution of incarceration to HCV transmission amongst PWID in Perry County (PC), Kentucky, USA, and the impact of scaling-up community and in-prison opioid substitution therapy (OST), including the potential for reducing incarceration. Methods: A dynamic model of incarceration and HCV transmission amongst PWID was calibrated in a Bayesian framework to epidemiological and incarceration data from PC, incorporating an empirically estimated 2.8-fold (95%CI: 1.36–5.77) elevated HCV acquisition risk amongst currently incarcerated or recently released (<6 months) PWID compared to other PWID. We projected the percentage of new HCV infections that would be prevented among PWID over 2020–2030 if incarceration no longer elevated HCV transmission risk, if needle and syringe programmes (NSP) and OST are scaled-up, and/or if drug use was decriminalized (incarceration/reincarceration rates are halved) with 50% of PWID that would have been imprisoned being diverted onto OST. We assume OST reduces reincarceration by 10–42%. Results: Over 2020–2030, removing the effect of incarceration on HCV transmission could prevent 42.7% (95% credibility interval: 15.0–67.4%) of new HCV infections amongst PWID. Conversely, scaling-up community OST and NSP to 50% coverage could prevent 28.5% (20.0–37.4%) of new infections, with this increasing to 32.7% (24.5–41.2%) if PWID are retained on OST upon incarceration, 36.4% (27.7–44.9%) if PWID initiate OST in prison, and 45.3% (35.9–54.1%) if PWID are retained on OST upon release. decriminalization (with diversion to OST) could further increase this impact, preventing 56.8% (45.3–64.5%) of new infections. The impact of these OST interventions decreases by 2.1–28.6% if OST does not reduce incarceration. Conclusion: Incarceration is likely to be an important contributor to HCV transmission amongst PWID in PC. Prison-based OST could be an important intervention for reducing this risk.