HIV Treatment and Prevention: A Simple Model to Determine Optimal Investment

Objective. To create a simple model to help public health decision makers determine how to best invest limited resources in HIV treatment scale-up and prevention. Method. A linear model was developed for determining the optimal mix of investment in HIV treatment and pre-vention, given a fixed budget. The model incorporates es-timates of secondary health benefits accruing from HIV treatment and prevention and allows for diseconomies of scale in program costs and subadditive benefits from con-current program implementation. Data sources were pub-lished literature. The target population was individuals infected with HIV or at risk of acquiring it. Illustrative ex-amples of interventions include preexposure prophylaxis (PrEP), community-based education (CBE), and antiretro-viral therapy (ART) for men who have sex with men (MSM) in the US. Outcome measures were incremental cost, quality-adjusted life-years gained, and HIV infec-tions averted. Results. Base case analysis indicated that it is optimal to invest in ART before PrEP and to invest in CBE before scaling up ART. Diseconomies of scale reduced the optimal investment level. Subadditivity of benefits did not affect the optimal allocation for rela-tively low implementation levels. The sensitivity analysis indicated that investment in ART before PrEP was opti-mal in all scenarios tested. Investment in ART before CBE became optimal when CBE reduced risky behavior by 4 % or less. Limitations of the study are that dynamic effects are approximated with a static model. Conclu-sions. Our model provides a simple yet accurate means of determining optimal investment in HIV prevention and treatment. For MSM in the US, HIV control funds should be prioritized on inexpensive, effective programs like CBE, then on ART scale-up, with only minima