The cost-effectiveness of interventions that provide human immunodeficiency virus (HIV) postexposure prophylaxis (PEP) to individuals after sexual or injection-drug use exposures depends on the distribution of exposure routes, prevalence of infection among source partners, adherence to PEP regimens, medical care costs, and prevailing epidemiologic contexts, among other factors. Objective: To determine the cost-effectiveness of a comprehensive program to prevent HIV infection after sexual or

more »

... ction-drug use exposure for 401 persons seeking PEP in an urban community. Methods: We conducted a retrospective cost analysis to evaluate the cost of the PEP intervention, then combined this information with model-based effectiveness estimates to determine the PEP program's "cost-utility ratio," which is the ratio of net program costs to the total number of quality-adjusted life-years (QALYs) saved by the program. Results: The average cost of the PEP regimen was $1222, and the total cost of the program was $450970. The PEP program prevented an estimated 1.26 HIV infections, saved 11.74 QALYs, and averted $281323 in future HIVrelated medical care costs. The overall cost-utility ratio was $14 449 per QALY saved. When analysis was restricted to men reporting receptive anal intercourse, the savings in averted HIV-related medical care costs exceeded the cost of the program. The results were generally robust to changes in key parameter values but were sensitive to assumptions about the HIV transmission probability for receptive anal intercourse. ORIGINAL INVESTIGATION