Purpose: Effective control of the global HIV epidemic requires judicious allocation of scarce resources between testing, treatment and prevention. Existing models used to inform the decision making process are too simplistic, while theoretical models are complex and impractical. Collaborating with UNAIDS, we designed a customizable, user-friendly model for decision making on HIV resource allocation that accounts for the effects of different levels of investment in interventions, effects of overlapping interventions, and epidemic dynamics.
Method: We created a spreadsheet-based model with a simple user interface. Default values characterizing the epidemic, key risk behaviors and available interventions are suggested for all parameters based on the literature. The user can customize these parameters. Epidemic dynamics are estimated by independent modules accounting for mother-to-child transmission (MTCT) and key risk groups: injection drug users (IDU), commercial sex workers (CSW) and men who have sex with men (MSM). Each module is designed as a dynamic compartmental model. Interventions considered include voluntary counseling and testing (VCT), HIV treatment (HAART), blood safety programs, prevention of MTCT, condom promotion, outreach for CSW and MSM, harm reduction (substitution therapy, needle exchange), and education. Production functions model program effect as a function of investment, and the effects of overlapping interventions are considered. The user inputs budget allocations that determine the scale of the interventions. The model estimates HIV prevalence, infections averted, QALYs gained and cost per QALY gained over a 20-year time horizon. The model also determines the optimal allocation of investment between interventions.
Result: We populated the model with data from Ukraine, Russia, Tanzania and Zambia. We calibrated our results against current practice in these countries and compared them against the optimized budget allocation. We showed that in Ukraine and Russia significant additional benefits can be obtained by increasing the budget allocation for harm reduction and treatment for IDUs. For heterosexually driven epidemics where concurrent partnerships occur, it may be optimal to increase investment in interventions that reduce the number of partners.
Conclusion: Our model provides a much needed bridge between research and practice, and can improve the HIV resource allocation process in settings around the world.
Candidate for the Lee B. Lusted Student Prize Competition