A reality check: the cost of making post-exposure prophylaxis available to gay and bisexual men at high sexual risk

The successful use of antiretroviral therapy for post-exposure prophylaxis (PEP) in cases of accidental and occupational exposures has prompted researchers, clinicians and public health decision makers to ask whether PEP would be effective in cases of sexual exposures. Although the answer to this question remains unknown, some factors that need to be considered have been identified. These include: the frequency of exposure, the probability of knowing the HIV status of the source, the elapsed time between exposure and possible intervention, and the impact PEP may have on risk reduction behaviours. In addition, given the limited resources available for the management of HIV disease, the cost of PEP will play a certain role in deciding its future. Other studies [1–3] have investigated whether using PEP for sexual exposures to HIV is effective. Pinkerton et al. [3] conducted an in-depth cost–utility analysis, and concluded that PEP should be recommended to partners of infected persons, to patients reporting unprotected anal intercourse, and possibly in cases in which there is a substantial likelihood that the partner is infected. In terms of clinical practice, no consensus has been established among physicians on the use of PEP for non-occupational exposures. Although some physicians are reluctant to prescribe antiretroviral prophylaxis, others appear to have a favourable attitude towards the prescription of PEP for sexual exposures [4] For example, in San Francisco, CA, USA, two clinics have recently opened and are currently providing anti-HIV prophylaxis after high-risk sexual exposures [5,6] In the light of the uncertainty surrounding this issue and its possible implications, leading commentators in the area have made a call for the development of rational guidelines [4,7] The following cost analysis is a step in this direction because the wise allocation of scarce resources is an integral part of any HIV management strategy. Although a few economic analyses have been conducted, no studies have investigated how much it would cost to provide PEP to a known at-high-sexual-risk population. The purpose of our study was to determine the cost of providing post-exposure prophylaxis to the male gay and bisexual community at high sexual risk of contracting HIV in the West End of Vancouver, British Columbia, Canada. A cost estimate was obtained by multiplying the cost of antiretroviral prophylaxis per course by the number of gay and bisexual men at high sexual risk and by the number of risk incidents per person per year. To determine how many men were at high risk, responses on a self-administered questionnaire given to a prospective cohort of gay and bisexual men beginning in May 1995 were used. High sexual risk was defined as having at least one episode of unprotected anal sex (insertive or receptive) with a casual male partner in the previous year, or having at least one episode of unprotected anal sex (insertive or receptive) with an HIV-positive man in the previous year. The proportion of men in the West End who identified themselves as either gay or bisexual was derived from a random telephone survey, and the cost of a course of PEP was taken from the British Columbia Centre for Excellence in HIV/AIDS Drug Treatment Program. Monte Carlo methods were used to simulate confidence limits around the cost estimate. Out of an estimated total of 5100 (95% confidence interval: 4700–5400) gay and bisexual men in Vancouver's West End, 1391 (27.3%) were classified as being at high risk of contracting HIV through unsafe sexual behaviours on the basis of prospective cohort data. The average number of risk incidents per person per year was three (0–6) and, depending on the recommended regimen, stavudine and lamivudine or triple therapy with nelfinavir, the average cost of PEP varied from Can$530 to 903 with an average price of Can$560. On the basis of these assumptions and the Monte Carlo simulation, the potential cost of making post-exposure prophylaxis available to all those at high sexual risk in the West End was estimated to be Can$2 259 780 (95% confidence interval: Can$800 000–4 100 000). The above minimum cost estimate, Can$800 000 per annum, for providing PEP to at-risk gay and bisexual men in Vancouver's West End is approximately equal to British Columbia's current budget for all accidental exposures in the province. This is an important fact considering the limited resources available to fight HIV disease and Canada's universal healthcare system. In light of the numerous uncertainties regarding the effectiveness of PEP for sexual exposures, the growing cost of providing anti-HIV therapy for confirmed positive individuals, and the potential cost of expanding the use of PEP to include high-risk consensual sex, we feel that other preventative strategies should take priority. Future research in this area is needed so that clinicians, researchers, policy makers and HIV-positive persons can gain a better sense of the issues surrounding and the implications of making PEP available for sexual exposures. Sophie Low-Beer Amy E. Weber Kim Bartholomew Monica Landolt Doug Oram Julio S. G. Montaner Michael V. O'Shaughnessy Robert S. Hogg

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