Universal eligibility for antiretroviral therapy (ART) in sub-Saharan Africa (SSA) has reduced HIV transmissions and deaths among people living with HIV (PLHIV). A growing proportion of transmissions and deaths now occur among PLHIV who have interrupted ART. Dozens of interventions to improve retention on ART have been proposed, but most of them cost more than standard-of-care. Research is needed to inform the upper-bound costs at which such interventions should be adopted.
We used three HIV models with diverse structures, assumptions, and settings: EMOD in South Africa, Optima in Malawi, and Synthesis in SSA lower-middle income countries (LMICs). Each model simulated reducing ART interruptions by 25%, 50%, or 100%, with or without targeting those most-at-risk of interruption, and with annual discount rates of 0%, 3%, or 6%. We compared infections averted, disability-adjusted life-years (DALYs) averted, and upper-bound costs at which improving ART retention could be cost-effective compared to alternative HIV program investments.
The three models simulated diverse epidemic trends and estimated different impact levels and timing of the impact of retention interventions (Figure 1). Despite these differences, the models produced consistent estimates of health benefit and transmission reduction per additional person-year retained on ART. The range of estimates was 1.35 ? 2.60 DALYs and 0.07 ? 0.16 infections averted over 40 years per additional person-year retained on ART over this period. Upper-bound cost that could be spent to retain an additional person on ART varied by setting and intervention effectiveness. Improving retention by 25% among all people receiving ART, regardless of ART interruption risk, had an upper-bound cost per person-year of US$2 ? $6 per person-year in Optima (Malawi), US$43 ? $68 in Synthesis (SSA LMICs), and US$28 ? $180 in EMOD (South Africa). A maximally targeted and effective retention intervention had an upper-bound cost per person-year of US$93 ? $223 in Optima (Malawi), US$871 ? $1,389 in Synthesis (SSA LMICs), and US$1,013 ? $6,518 in EMOD (South Africa).
Across diverse settings and assumptions, three HIV models provided consistent estimates of the health and transmission benefits of improving retention in SSA. Upper-bound costs that could be spent to improve ART retention vary across SSA settings and could be increased by targeting interventions to those most at-risk of interrupting ART.