THE RELATIVE IMPACTS OF ANTIRETROVIRAL THERAPY AND HARM REDUCTION INITIATIVES ON HIV INCIDENCE IN BRITISH COLUMBIA, CANADA: 1996-2013

Purpose: Access to antiretroviral therapy and harm reduction services have been cited as key contributors to the control of the HIV epidemic, however the specific contribution of the latter has been questioned due to uncertainty in the true efficacy of ART in prevention HIV transmission through needle sharing.  We aimed to isolate the independent effects of the provision of opioid agonist treatment (OAT) and needle distribution (or harm reduction services), and the secondary preventive benefits of ART through needle sharing on HIV incidence in British Columbia, from 1996-2013. 

Methods: Using comprehensive linked population-level data, we populated a dynamic, compartmental transmission model to simulate the HIV/AIDS epidemic in BC from 1996-2013. HIV incidence, mortality among PLHIV, and quality-adjusted life years (QALYs) were estimated. We further incorporated rates of OAT utilization and syringe distribution volumes to estimate their impact on the selected outcomes.  We estimated scenarios designed to isolate the independent effects of ART on transmission via needle-sharing (assuming 50% (10%-90%) efficacy) and harm reduction services in reducing HIV incidence through needle sharing– both among PWID and at the population-level. Structural and parameter uncertainty was investigated.

Results: We estimated that 3240 (2394-4562) incident HIV cases were averted between 1996 and 2013 as a result of the combined effect of the expansion of harm reduction services and ART coverage on HIV transmission via needle sharing.  Decomposing the effects of these services, we estimate harm reduction services alone would have accounted for 77% (62%-95%) of averted HIV incidence, while ART alone would have accounted for 44% (10%-67%) of incident cases. Due to high distribution volumes, provision of sterile syringes predominantly accounted for incidence reductions attributable to harm reduction services, however OAT provided substantially greater QALY gains.

Conclusion: The scale-up of harm reduction services had a profound impact on the course of the HIV epidemic in BC, with an impact on HIV incidence comparable to ART access. Harm reduction services such as needle distribution and OAT should be viewed as critical and cost-effective tools in a combination implementation strategy to reduce the public health and economic burden of HIV/AIDS.