Modelling the impact of prevention and treatment interventions on HIV and Hepatitis C virus transmission among PWID in Nairobi

Background

Kenya has one of the largest HIV epidemics in the world with HIV prevalence among people who inject drugs (PWID) far exceeding that of the general population. As in other settings in Sub-Saharan Africa, there is an emerging HCV epidemic among PWID, with antibody prevalence of 11-36%. Needle and syringe programmes (NSP) have scaled-up rapidly since 2013 and pilot HCV treatment programs for PWID are ongoing; however, opiate substitution therapy (OST) coverage is low. We model the impact of existing and scaled-up interventions on HIV/HCV transmission among PWID in Nairobi.

Methods

We developed a dynamic model of HIV/HCV transmission among PWID, calibrated to data from Nairobiand the Coastal region of Kenya on HIV (14% and 20%, respectively in 2012) and HCV prevalence (11-13% and 24-36% in 2015). We projected the impact of existing levels of interventions and the impact by 2030 of scaling-up OST to 50% and NSP to 75% (full harm reduction; full HR), and/or scaling-up HIV and HCV treatment; achieving UNAIDS 90-90-90 target for ART among PWID or treating 1,000 HCV+ve PWID over before 2024.

Results

The model projects that since their implementation, interventions have averted 10.5% (95%CrI: 8.0-12.6) and 31.2% (95%CrI: 26.1-35.4) of new HIV and HCV infections in Nairobi and 23.9% (95%CrI: 21.4-25.6) and 34.6% (95%CrI: 31.2-40.5) of new HIV and HCV infections in the Coastal region. Full HR and ART could reduce HIV incidence and HCV incidence by 46.2% (95%CrI: 37.6-54.6) and 66.0% (46.7-75.9%) by 2030 in Nairobi and 70.0% (95%CrI: 62.5-75.9) and 95.1% (95%CrI: 91.3-96.6) in the Coastal region, respectively. If HCV treatment is also scaled-up, then HCV incidence in Nairobi could reduce by 96.6% (95%CrI: 82.6-99.3) by 2030.

Conclusion

Existing interventions may have had moderate impact on HIV and HCV transmission in Kenya. Scaled-up harm reduction and ART may achieve significant reductions in HIV incidence, but interventions that reduce sexual risk may also be required, particularly in Nairobi. Scaled-up harm reduction could achieve HCV elimination targets in the Coastal region but significant levels of HCV treatment with DAAs will also be required to achieve these targets in Nairobi.