February 26, 2009
"The combination of tenofovir and emtricitabine shows promise as HIV pre-exposure prophylaxis (PrEP)," noted the authors, who undertook the current study to forecast the clinical, epidemiological, and economic outcomes of PrEP, "taking into account uncertainties regarding efficacy, the risks of developing drug resistance and toxicity, behavioral disinhibition, and drug costs."
To model PrEP among US men who have sex with men, the researchers adapted a computer simulation of HIV acquisition, detection, and care. Base-case assumptions included 50 percent efficacy of PrEP and monthly tenofovir-emtricitabine costs of $753. Sensitivity analyses were employed to examine stability of results and to identify critical input parameters.
In a cohort with a mean age of 34 years, the results showed PrEP reduced lifetime HIV infection risk from 44 percent to 25 percent and increased mean life expectancy from 39.9 to 40.7 years (21.7 to 22.2 discounted quality-adjusted life-years). "Discounted mean lifetime treatment costs increased from $81,100 to $232,700 per person, indicating an incremental cost-effectiveness ratio of $298,000 per quality-adjusted life-year gained," the authors wrote.
When greater (90 percent) PrEP efficacy was assumed, markedly larger reductions in lifetime infection risk (from 44 percent to 6 percent) were noted. Targeting younger populations with a higher incidence of infection and improvements in the cost and efficacy of PrEP yielded more favorable incremental cost-effectiveness ratios.
"PrEP could substantially reduce the incidence of HIV transmission in populations at high risk of HIV infection in the United States," the authors concluded. "Although it is unlikely to confer sufficient benefits to justify the current costs of tenofovir-emtricitabine, price reductions and/or increases in efficacy could make PrEP a cost-effective option in younger populations or populations at a higher risk of infection. Given recent disappointments in HIV infection prevention and vaccine development, additional study of PrEP-based HIV prevention is warranted."