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. 2017 Apr 12;12(4):e0175447.
doi: 10.1371/journal.pone.0175447. eCollection 2017.

The potential impact and cost of focusing HIV prevention on young women and men: A modeling analysis in western Kenya

Ramzi A Alsallaq  1 , Jasmine Buttolph  1 , Charles M Cleland  1 , Timothy Hallett  2 , Irene Inwani  3 , Kawango Agot  4 , Ann E Kurth  1
Affiliations

The potential impact and cost of focusing HIV prevention on young women and men: A modeling analysis in western Kenya

Ramzi A Alsallaq et al. PLoS One. .

Abstract

Objective: We compared the impact and costs of HIV prevention strategies focusing on youth (15-24 year-old persons) versus on adults (15+ year-old persons), in a high-HIV burden context of a large generalized epidemic.

Design: Compartmental age-structured mathematical model of HIV transmission in Nyanza, Kenya.

Interventions: The interventions focused on youth were high coverage HIV testing (80% of youth), treatment at diagnosis (TasP, i.e., immediate start of antiretroviral therapy [ART]) and 10% increased condom usage for HIV-positive diagnosed youth, male circumcision for HIV-negative young men, pre-exposure prophylaxis (PrEP) for high-risk HIV-negative females (ages 20-24 years), and cash transfer for in-school HIV-negative girls (ages 15-19 years). Permutations of these were compared to adult-focused HIV testing coverage with condoms and TasP.

Results: The youth-focused strategy with ART treatment at diagnosis and condom use without adding interventions for HIV-negative youth performed better than the adult-focused strategy with adult testing reaching 50-60% coverage and TasP/condoms. Over the long term, the youth-focused strategy approached the performance of 70% adult testing and TasP/condoms. When high coverage male circumcision also is added to the youth-focused strategy, the combined intervention outperformed the adult-focused strategy with 70% testing, for at least 35 years by averting 94,000 more infections, averting 5.0 million more disability-adjusted life years (DALYs), and saving US$46.0 million over this period. The addition of prevention interventions beyond circumcision to the youth-focused strategy would be more beneficial if HIV care costs are high, or when program delivery costs are relatively high for programs encompassing HIV testing coverage exceeding 70%, TasP and condoms to HIV-infected adults compared to combination prevention programs among youth.

Conclusion: For at least the next three decades, focusing in high burden settings on high coverage HIV testing, ART treatment upon diagnosis, condoms and male circumcision among youth may outperform adult-focused ART treatment upon diagnosis programs, unless the adult testing coverage in these programs reaches very high levels (>70% of all adults reached) at similar program costs. Our results indicate the potential importance of age-targeting for HIV prevention in the current era of 'test and start, ending AIDS' goals to ameliorate the HIV epidemic globally.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Calibration of model parameters using epidemiological and behavioral data from Nyanza.
A) Calibration of model uncertain parameters using age-gender-specific prevalence data at different years from Kenya's KDHS 2003 and 2008/09 and KAIS 2007 surveys [17,53,54] and a published report by Amornkul et. al. [55]. Dark blue lines indicate confidence intervals of prevalence data. Prevalence values among males and females of various age intervals are indicated with M and F otherwise no indication for values among all adults of that age. Calibration to B) age-specific data on numbers ever initiated treatment up to 2009 as reported in NASCOP 2009 report [46], and to C) age-gender-specific data on numbers ever initiated treatment during 2011 from NASCOP [42]. Calibrations in B) and C) are used to adjust proportion initiating treatment at CD4 = 350 and at CD4≤250 cells/mm3 in fitted case (estimated at 10% and 90% of those with CD4≤350 cells/mm3, respectively). D) Assumed baseline male circumcision coverage among young men representing recent increase in proportion of young males (age 15–24) getting circumcised in Nyanza [46,54,56,57] (incorporated in the fitted case and all scenarios).
Fig 2
Fig 2. A schematic outlining our analysis.
Comparison scenarios depicted in the three bottom boxes connected by the decision making solid lines are incremental to the scenario shown in the top box of: 1) 40% HIV testing among adults ages≥15 and prompt initiation of ART at CD4 ≤350 cells/mm3 2) undiagnosed infected persons presenting late to care/initiating treatment at CD4 ≤250 cells/mm3, and 3) male circumcision uptake of 37%. The comparison scenarios focusing on adults consisted of increased HIV testing among adults (from 40% up to 80% coverage) and provision of TasP and condoms. The rest of the comparison scenarios depicted in shaded blocks focus on youth where in one set HIV testing coverage is increased specifically among youth to 80% and diagnosed youth are provided TasP while condoms were provided to all newly diagnosed persons and all other baseline services are kept (Table 2). In the other set of scenarios beside the previous scenario of 80% testing coverage among youth with TasP/condoms, gender-age-tailored interventions for susceptible youth are combined at various coverage and/or efficacy values (Table 3).
Fig 3
Fig 3
Comparison of cumulative impact and costs over (A) 5 years and (B) 20 years of youth-focused scenario (upward triangle) to adult-focused scenarios. The youth-focused scenario consists of 80% testing coverage among youth and providing TasP and condoms to HIV-diagnosed youth as well as prompt treatment at CD4≤350 cells/mm3 and condoms for HIV-diagnosed adults. Adult-focused scenarios encompass increased testing among adults and providing only TasP and condoms. The details of the six intervention scenarios compared here are in Table 2. The resulting cost frontiers (lines through red points) from cost-effectiveness analyses using DALYs averted (top-row) and infections averted (bottom-row) are shown along with the dominated scenarios (blue points). The estimates are shown at year 5 in panel A and at year 20 in panel B. Dominated scenarios comparatively cost more US$ per DALY averted (top-row) or more US$ per infection averted (middle-row). M = million.
Fig 4
Fig 4
Comparison of cumulative impact and costs over (A) 5 years and (B) 20 years of youth-focused to adult-focused scenarios. Youth-focused scenarios are based on 80% testing coverage among youth and providing TasP for HIV-diagnosed youth and condoms to newly diagnosed persons in addition to age-gender-risk targeted interventions to HIV-susceptible youth. Adult-focused scenarios encompass increased testing among adults and providing only TasP and condoms following diagnosis with HIV. The comparison involved 65 scenarios but in the plots, only potentially cost-effective scenarios (red colored points) and selected dominated scenarios (blue colored points) are shown. Cost frontiers (lines through red points) are shown in terms of DALYs averted and infections averted (top and bottom figures, respectively) at 5 and 20 years (A and B panels, respectively). M = million.
Fig 5
Fig 5
Comparison of cumulative impact and costs over 35 years of youth-focused to adult-focused scenarios with (A) default annual care costs per person in late stages of HIV and (B) when these care costs are much higher. The comparison involved 65 scenarios but in the plots, only potentially cost-effective scenarios (red colored points) and selected dominated scenarios (blue colored points) are shown. Cost frontiers (lines through red points) are shown in terms of DALYs averted and infections averted (top and bottom figures, respectively) at 5 and 20 years (A and B panels, respectively). M = million.
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