Purpose: Understanding how to balance investments in prevention versus treatment for HIV is a worldwide public health priority. Our aim was to develop a general framework to guide allocation of resources among portfolios of HIV prevention and treatment interventions.

Methods: We created a dynamic HIV transmission model with 480 compartments to estimate health costs and quality-adjusted life years (QALYs), as well as new infections and disease prevalence over time. We stratified the population by gender, risk behavior, and HIV infection status. The model can assess portfolios of interventions, including HIV screening, treatment with highly active antiretroviral therapy (HAART), preventive and therapeutic vaccines, and male circumcision. As example interventions, we compared the cost-effectiveness of an imperfect preventive vaccine to strategies that expand the use of HAART for U.S. populations. We estimated the benefits and costs of HAART from published data, and evaluated potential vaccines of varying effectiveness.

Results: A preventive vaccine with 75% efficacy, lifetime duration, and price of $1000 that is given to 50% of all uninfected individuals prevented 2.4 million HIV infections over 20 years, and added 3 million QALYs at a cost of $53,000 per QALY gained. At a vaccine price of $500, this strategy cost $15,000 per QALY gained; at a price of $425, this strategy cost $8,950 per QALY gained. Strategies to expand the use of HAART from a current average level of 65% to 85% prevented 433,000 HIV infections, and added 1.8 million QALYs at a cost $8,900 per QALY gained. The cost of vaccinating 50% of the population (at a price of $500) was approximately triple the amount needed to scale up HAART; however, the vaccine strategy prevented five times more infections and provided two times more QALYs than the treatment strategy. Allocation of resources to both interventions produced outcomes intermediate to those that occur with investment exclusively in prevention or treatment.

Conclusions: A partially effective vaccine could prevent a significant number of HIV infections and provide additional health benefits. The cost-effectiveness of HIV vaccination strategies are comparable to those obtained from expanding HAART, provided that the vaccine price is sufficiently low. Our model provides a general framework for understanding the health and economic outcomes associated with varying investments in portfolios of HIV prevention and treatment interventions.