Modelling the Impact of Prevention and Treatment Interventions on HIV and Hepatitis C Virus Transmission Among People Who Inject Drugs in Kenya

Background: People who inject drugs (PWID) in Kenya have a high prevalence of HIV (14-26%) and HCV (11-36%). Needle and syringe programmes (NSP) and antiretroviral therapy (ART) have high coverage among PWID, while HCV treatment and opioid substitution therapy (OST) access is low. Methods: A dynamic model of HIV (sexual and injecting-related) and HCV (injecting-related) transmission among PWID was calibrated using Bayesian methods to data from Nairobi and the Coastal region. We projected the impact of existing coverage levels of interventions (ART: 64-66%; OST: 4-7%; NSP: 54-56%) in each setting, and the impact over 2020-2030 of increasing the coverage of OST (50%) and NSP (75%; full HR), ART (UNAIDS 90-90-90 target), HCV treatment (1000 over 5 years), and reducing HIV sexual risk by 75%. We estimated HCV treatment levels needed to reduce HCV incidence by 90% with or without full HR. Findings: Since 2013, HR has averted 15.1-20.6% (range in medians across settings) of HIV infections and 29.0-31.6% of HCV infections across Nairobi and the Coastal region, with most impact being due to NSP. Conversely, ART has only averted <5% of HIV infections since 2004 because of sub-optimal viral suppression (28-48%). Going forward, Full HR and ART could reduce HIV incidence by 58.2-62.0% and HCV incidence by 62.6-81.6% by 2030 across these settings. If sexual risk is also reduced, HIV incidence would reduce by 77.1-81.4%. Alongside full HR, treating 896 PWID over 2020-2025 could reduce HCV incidence by 90% by 2030. Interpretation: Existing interventions have had moderate impact on HIV and HCV transmission in Kenya, but may have substantial impact if scaled-up. However, to achieve HIV and HCV elimination, reductions in sexual risk are needed and a scale-up in HCV treatment.