Cost-effectiveness of chemoprophylaxis after occupational exposure to HIV

To assess the economic efficiency of recent US Public Health Service recommendations for chemoprophylaxis with a combination of antiretroviral drugs following high-risk occupational exposure to human immunodeficiency virus (HIV). To provide a framework for evaluating the relative effectiveness and costs associated with candidate postexposure prophylaxis (PEP) regimens.

Standard techniques of cost-effectiveness and cost-utility analysis were used. The analysis compares the costs and consequences of a hypothetical, voluntary combination-drug PEP program consisting of counseling for all HIV-exposed health care workers, followed by chemoprophylaxis for those who elect it vs an alternative in which PEP is not offered. A societal perspective was adopted and a 5% discount rate was used. Hospital costs of recommended treatment regimens (zidovudine alone or in combination with lamivudine and indinavir) were used, following the dosing schedules recommended by the US Public Health Service. Estimates of lifetime treatment costs for HIV and acquired immunodeficiency syndrome were obtained from the literature. Because the effectiveness of combination PEP has not been established, the effectiveness of zidovudine PEP was used in the base-case analyses.

Net PEP program costs, number of HIV infections averted, cost per HIV infection averted, and cost-utility ratio (net cost per discounted quality-adjusted life-year saved) for zidovudine, lamivudine, and indinavir combination PEP. Lower bounds on the effectiveness required for combination regimens to be considered incrementally cost saving, relative to zidovudine PEP alone, were calculated. Multiple sensitivity and threshold analyses were performed to assess the impact of uncertainty in key parameters.

Under base-case assumptions, the net cost of a combination PEP program for a hypothetical cohort of 10,000 HIV-exposed health care workers is about $4.8 million. Nearly 18 HIV infections are prevented. The net cost per averted infection is just less than $400,000, which exceeds estimated lifetime HIV and acquired immunodeficiency syndrome treatment costs. Although combination PEP is not cost saving, the cost-utility ratio (about $37,000 per quality-adjusted life-year in the base case) is within the range conventionally considered cost-effective, provided that chemoprophylaxis is delivered in accordance with Public Health Service guidelines. Small incremental improvements in the effectiveness of PEP are associated with large overall societal savings.

Under most reasonable assumptions, chemoprophylaxis with zidovudine, lamivudine, and indinavir following moderate- to high-risk occupational exposures is cost-effective for society. If combination PEP is minimally more effective than zidovudine PEP, then the added expense of including lamivudine and indinavir in the drug regimen is clearly justified.