With an adult prevalence of 31%, Swaziland has a severe, generalized HIV epidemic. Despite behavior change and other prevention programs, including scale-up of antiretroviral therapy (ART), new infections continue to be a problem, especially in young women (where incidence is 4.2%). The importance of population-specific combination prevention approaches to HIV has made mathematical modeling a necessary tool for planning efforts. As part of the evaluation of policy measures to end Swaziland’s HIV epidemic by 2030, we modeled the efficacy and cost effectiveness of various treatment and prevention strategies.
Using demographic and epidemiological data from Swaziland, we constructed dynamic compartmental models as well as network models to assess the impact of ART scale-up as well as PrEP offered to 10% of the highest risk population over the next 15 years.
Continuing the status quo—where ~$110 million is spent yearly on HIV programs and the median CD4 at initiation is 234—will yield 10.5 million quality-adjusted life years (QALYs) between 2015-30. For an added $110 million over 15 years, another 300,000 QALYs can be gained by offering PrEP to 10% of the highest risk population. This represents a cost of $366 per QALY gained. Compared to status quo, scale up of ART to CD4 < 350 yields an additional 800,000 QALYs at $288 per QALY gained, while universal ART coverage yields an additional 1.5 million QALYs at $327 per QALY gained. Figure 1 shows the potential benefit of PrEP delivered to one high-risk group in particular—young women—over the next 15 years.
In the current setting of low median CD4 at ART initiation, immediate role-out of PrEP to 10% of the highest risk population is very cost-effective at $366 per QALY gained. As the country gets to 100% test and treat, however, PREP is no longer cost effective. Since scale up of ART to universal coverage will take many years, there is impetus to roll out PREP to populations where both risk and PREP adherence are deemed to be highest. This strategy is also supported by the most recent WHO guidelines, which recommend offering PrEP “to people at substantial risk of HIV infection,” specified as >3% incidence. Given the significant preventive benefit of ART scale-up, however, an important caveat for PrEP programs is that they should be rolled out only if they do not detract from existing ART programs or future ART scale-up.