A COST-EFFECTIVENESS ANALYSIS OF PRE-EXPOSURE PROPHYLAXIS (PrEP) FOR THE PREVENTION OF HIV IN THE LOS ANGELES COUNTY MSM POPULATION

Importance: The clinical safety and efficacy of pre-exposure prophylaxis (PrEP) as well as early initiation of HIV treatment for preventing infection with the human immunodeficiency virus (HIV) has been demonstrated in clinical studies. However substantial gaps still remain in our understanding of the potential trade-offs between aggressive screening of HIV (“testing”), early initiation of treatment with antiretroviral therapy – ART (“test and treat”), and PrEP in controlling the disease in concentrated epidemic environments such as those of the men who have sex with men (MSM) population in Los Angeles County (LAC). More comprehensive cost-effectiveness analysis (CEA) studies are thus needed to guide public policy decisions for effective HIV prevention.

Objective: To assess the cost-effectiveness of the testing (expanded HIV screening), test and treat (early initiation and expanded coverage of ART) and PrEP strategies in preventing HIV among LAC MSMs.

Design, Setting, Population and Data: A compartmental mathematical model is developed to simulate the incidence of HIV among 15-65 year old MSMs of LAC over a twenty-year period.  An economic model uses the epidemic model results to estimates the cost and effectiveness of various HIV interventions using a societal perspective and a lifetime horizon. Annual population data (2000-2010) for the LAC MSM population are estimated from the LAC HIV Surveillance Reports and the RAND California Population and Demographics database. Input parameters and ranges for the models are derived from the published clinical literature, following a systematic review approach, the Federal Supply Schedule and the IMS Fee Schedule.

Main Outcome Measures: For each intervention, the number of new HIV infections averted, the discounted costs and quality-adjusted life years (QALYs), and the incremental cost-effectiveness ratios are estimated.

Results: Our preliminary base case results suggest that relative to the status quo policy, and at the current US willingness to pay threshold of $100,000/QALY saved, both the PrEP, testing and test and treat strategies are cost-effective. The first result is imputable to the protective benefits of PrEP, which averts secondary infections by acting as an “imperfect vaccine”, thereby offsetting the high cost of PrEP. The second result is a consequence of the reduction in risk behavior among infected individuals who become aware of their HIV status following testing. The last result derives from the combined survival and preventive benefits of testing and early treatment, which outweigh the cost of the intervention. Robustness analyses over parameter uncertainty ranges find the relative effectiveness of PrEP to be sensitive to PrEP adherence and uptake rates. All cost-effectiveness profiles improve with reductions in ART price following patent expiration and generic entry. The ICER estimates remain robust to other epidemic, cost, and effectiveness parameter values.

Conclusions: Both PrEP, testing and test and treat offer cost-effective alternatives to the status-quo policy in reducing HIV/AIDS among the LAC MSMs. The success of the PrEP and test and treat strategies remains particularly contingent on the uptake rate and adherence to treatment. Given the lack of evidence on adherence behaviors towards PrEP, further studies that mimic real-world adherence patterns are warranted.