Comparative effectiveness and cost-effectiveness of antiretroviral therapy and pre-exposure prophylaxis for HIV prevention in South Africa

Abstract

Background: Antiretroviral therapy (ART) and oral pre-exposure prophylaxis (PrEP) are effective in reducing HIV transmission in heterosexual adults. The epidemiologic impact and cost-effectiveness of combined prevention approaches in resource-limited settings remain unclear.

Methods: We develop a dynamic mathematical model of the HIV epidemic in South Africa's adult population. We assume ART reduces HIV transmission by 95% and PrEP by 60%. We model two ART strategies: scaling up access for those with CD4 counts ≤ 350 cells/μL (Guidelines) and for all identified HIV-infected individuals (Universal). PrEP strategies include use in the general population (General) and in high-risk individuals (Focused). We consider strategies where ART, PrEP, or both are scaled up to 100% of remaining eligible individuals yearly. We measure infections averted, quality-adjusted life-years (QALYs) gained and incremental cost-effectiveness ratios over 20 years.

Results: Scaling up ART to 50% of eligible individuals averts 1,513,000 infections over 20 years (Guidelines) and 3,591,000 infections (Universal). Universal ART is the most cost-effective strategy at any scale ($160-$220/QALY versus comparable scale Guidelines ART expansion). General PrEP is costly and provides limited benefits beyond ART scale-up ($7,680/QALY to add 100% PrEP to 50% Universal ART). Cost-effectiveness of General PrEP becomes less favorable when ART is widely given ($12,640/QALY gained when added to 100% Universal ART). If feasible, Focused PrEP is cost saving or highly cost effective versus status quo and when added to ART strategies.

Conclusions: Expanded ART coverage to individuals in early disease stages may be more cost-effective than current guidelines. PrEP can be cost-saving if delivered to individuals at increased risk of infection.

Figure 1

HIV infections averted and incremental costs versus the status quo with 100% scale-up for single or combination programs over 20 years. (A) Infections averted over 20 years with 100% scale-up for single or combination programs. (B) Incremental costs versus status quo over 20 years with 100% scale-up for single or combination programs. Strategies include: Guidelines ART (individuals with CD4 cell counts ≤350 cells/μL only), Universal ART (all HIV-infected individuals), General PrEP (general population), and Focused PrEP (individuals at high risk of acquiring HIV). Bars 1 and 2 show results of ART programs alone, 3 and 4 show results of PrEP programs alone, and bars 5 to 8 show results of pairwise combinations of ART and PrEP programs. ART strategies indicated by bar color: Guidelines - red; Universal - orange; Status quo - no color. PrEP strategies indicated by bar outline: General - solid line; Focused - dashed line; Status quo - no line.

Figure 2

Infections averted over 20 years with portfolios of scaled-up ART and PrEP. (A) Infections averted over 20 years with portfolios of scaled-up Guidelines ART (individuals with CD4 cell counts ≤ 350 cells/μL only) and General PrEP (general population). (B) Infections averted over 20 years with portfolios of scaled up Universal ART (all HIV-infected individuals) and General PrEP (general population).

Figure 3

Cost-effectiveness (quality-adjusted life-years versus total costs over 20 years) of 100% scale-up for single or combination programs. Guidelines ART (individuals with CD4 cell counts ≤350 cells/μL only), Universal ART (all HIV-infected individuals), General PrEP (general population), Focused PrEP (individuals at high risk of acquiring HIV). ART strategies indicated by dot shape: Guidelines - triangle; Universal - diamond; Status quo - X mark. PrEP strategies indicated by dot color: General - black; Focused - gray. There is no PrEP in the status quo.