UBC Faculty Research and Publications

The relative impacts of antiretroviral therapy and harm reduction initiatives on HIV incidence in British Columbia, Canada, 1996-2013 : A modeling study Nosyk, Bohdan; Zang, Xiao; Min, Jeong Eun; Krebs, Emanuel; Lima, Viviane Dias; Milloy, M-J; Shoveller, Jean; Barrios, Rolando; Harrigan, Paul Richard; Kerr, Thomas; Montaner, Julio; Wood, Evan

Abstract

Background—Antiretroviral therapy (ART) 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 on HIV transmission through needle sharing. Using provincial data on OAT uptake and needle distribution volumes, we aimed to isolate the independent effects of harm reduction services and ART on HIV transmission via needle sharing 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, and quality-adjusted life years (QALYs) were estimated. We estimated scenarios designed to isolate the independent effects of harm reduction services and ART (assuming 50% (10%–90%) efficacy) in reducing HIV incidence through needle sharing. Structural and parameter uncertainty was investigated. Findings—We estimated that 3204 (2402–4589) 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. In a hypothetical scenario assuming ART had zero effect on transmission through needle sharing, we estimated harm reduction services alone would have accounted for 77% (62%–95%) of averted HIV incidence. In a separate hypothetical scenario where harm reduction services remained at 1996 levels, we estimated ART alone would have accounted for 44% (10%–67%) of averted HIV incidence. Due to high distribution volumes, needle distribution predominantly accounted for incidence reductions attributable to harm reduction, however OAT provided substantially greater QALY gains. Interpretation—If the true efficacy of ART in preventing HIV transmission through needle sharing is closer to its efficacy in sexual transmission, ART’s impact on incident cases averted may be greater than that of harm reduction. Nonetheless, harm reduction services played a vital role in reducing HIV incidence in BC, and should be viewed as critical and cost-effective tools in combination implementation strategies to reduce the public health and economic burden of HIV/AIDS.

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