Modelling the contribution of incarceration and public health oriented drug law reform to HCV transmission and elimination among PWID in Tijuana, Mexico

Background: Incarceration is associated with increased risk of hepatitis C virus (HCV) among people who inject drugs (PWID). Mexico's previous attempt in implementing a public health-oriented drug law reform resulted in minimal impact on incarceration among PWID. However, implementation of reforms alongside Mexico's HCV elimination program has the potential to reshape the HCV epidemic among PWID in the next decade. We use data from a cohort of PWID in Tijuana, Mexico, to inform epidemic modeling to assess the contribution of incarceration and fully implemented drug reform on HCV transmission and elimination among PWID.Methods: We developed a dynamic, deterministic model of incarceration, HCV transmission and disease pro-gression among PWID. The model was calibrated to data from Tijuana, Mexico, with 90% HCV seroprevalence among 10,000 PWID. We estimated the 10-year population attributable fraction (PAF) of incarceration to HCV incidence among PWID and simulated, from 2022, the potential impact of the following scenarios: 1) decrimi-nalization (80% reduction in incarceration rates); 2) fully implemented drug law reform (decriminalization and diversion to opiate agonist therapy [OAT]); 3) fully implemented drug law reform with HCV treatment (direct -acting antivirals [DAA]). We also assessed the number DAA needed to reach the 80% incidence reduction target by 2030 under these scenarios.Results: Projections suggest a PAF of incarceration to HCV incidence of 5.4% (95% uncertainty interval [UI]:0.6-11.9%) among PWID in Tijuana between 2022-2032. Fully implemented drug reforms could reduce HCV inci-dence rate by 10.6% (95%UI:3.1-19.2%) across 10 years and reduce the number of DAA required to achieve Mexico's HCV incidence reduction goal by 14.3% (95%UI:5.3-17.1%).Conclusions: Among PWID in Tijuana, Mexico, incarceration remains an important contributor to HCV transmis-sion. Full implementation of public health-oriented drug law reform could play an important role in reducing HCV incidence and improve the feasibility of reaching the HCV incidence elimination target by 2030.