Oral presentation at the 8th annual Canadian Conference on HIV/AIDS Research, in May 1999, in Victoria, BC.

The Cost of Providing Post-Exposure Prophylaxis for Gay and Bisexual Men at Non-Occupational Risk of Contracting HIV in the West End of Vancouver

Sophie Low-Beer, Amy E. Weber, Steve Martindale, K. Bartholomew, Keith Chan, M. Landolt, D. Oram, Michael V. O'Shaughnessy, Robert S. Hogg.

Psychology Department, Simon Fraser University;
and the British Columbia Centre for Excellence in HIV/AIDS, University of British Columbia, St. Paul's Hospital, Vancouver, Canada.

View presentation in Adobe PDF format

ABSTRACT:

Objective: To determine the cost of providing post-exposure prophylaxis to gay and bisexual men at high non-occupational risk of contracting HIV in Vancouver's West End.

Methods: The cost of non-occupation post-exposure prophylaxis was obtained by multiplying the cost of antiretroviral prophylaxis per course by the number of gay and bisexual men at non-occupation risk and by the average number non-occupational incidents per person per year. Non-Occupation risk was based on the proportion of Vanguard participants who had at least one episode of unprotected anal sex with a casual male partner in the previous year, or who reported having unprotected anal sex with someone they knew at the time was HIV positive. The cost of post-exposure prophylaxis was taken from the HIV/AIDS Drug Treatment Program. The proportion of the West End male population 20 years and over estimated to be gay or bisexual was derived from a random telephone survey. Monte Carlo trials were used to simulate the confidence limits around our cost estimate.

Results: The gay and bisexual male population in the West End was estimated to be 5,100. Based on Vanguard data we estimated that 1391 individuals (27.3%) in this population would be at non-occupation risk for HIV. The average number of incidents per year was three. The average cost for antiretroviral prophylaxis therapy was $560 with the range being $530 for double and $903 for triple therapy. The potential non-occupational post-exposure prophylaxis to all those at risk in the West End was estimated to be $2,400,000 (95% CI: $800,000 - $4,100,000).

Conclusion: Our results indicate that providing post-exposure prophylaxis for those at high sexual risk of contracting HIV would cost a minimum of $800,000 per year. It is important to consider that this figure alone is approximately equal to the province's current budget for accidental and occupational post-exposure prophylaxis.

 

Background

Guideline for Accidental Exposure to HIV

  • Occupational Exposures
  • Community Exposures

Recommended Regimen

  • Stavudine (d4T)
  • Lamivudine (3TC)
  • Nelvfinavir (in cases of higher risk)

 

Probability of Transmission From one HIV Exposure

  • Intravenous needle/syringe = 0.67 %
  • Needlestick (percutaneous) = 0.4 %
  • Receptive anal intercourse = 0.1 - 3.0 %
  • Receptive vaginal intercourse = 0.1 - 0.2 %

 

Question

Considering that unprotected anal receptive intercourse with an HIV positive individual carries the greatest risk of transmission why don't current therapeutic guidelines advocate for the use of post-exposure prophylaxis for sexual exposures?

 

The Differences Between Occupational and Non-Occupational Exposures

  • Frequency of exposure
  • Probability of knowing HIV status of source
  • Elapsed time between incident and intervention
  • Effectiveness
  • Effects on risk reduction behaviour

 

Objective

To determine the cost of providing post-exposure prophylaxis to gay and bisexual men at high non-occupational risk of contracting HIV in the West End of Vancouver.

 

 

Methods

The proportion of the West End male population over 20 years of age estimated to be gay or bisexual was derived from a random telephone survey.

 

Vanguard Project Eligibility Criteria

  • 15 to 30 years old at baseline
  • Living in Greater Vancouver area
  • Gay, bisexual, and/or MSM
  • No previous HIV-positive test result

 

Definition

High Non-Occupational Risk:

  • at least one episode of unprotected anal sex with a casual male partner in the previous year

OR

  • at least one episode of unprotected anal sex with an HIV-positive male in the previous year

 

Results

  • Gay and bisexual population in West End = 5,057
  • Percentage of Vanguard at non-occ. risk = 26.6 %
  • West End population at non-occ. risk = 1,345
  • Average number of at risk incidents/year = 3
  • Average cost of 1 month course of PEP = $560.00

 

Monte Carlo Simulation Assumptions

  1. % at non-occupational risk
    mean = 26.6 %, range = 20.6 - 32.6, normal distribution
  2. Post-exposure prophylaxis cost
    mean = $560, range = $532 - $903, weibull distribution
  3. # of risk incidents/year
    mean = 3, range = 0 - 6, normal distribution

 

Result of Monte Carlo Trials

The potential cost of providing post-exposure prophylaxis for all those at non-occupational risk in the West End was estimated at : $ 2,259,780 (95 % Cl = $800,000 - $4,100,000).

 

Conclusions

Our results indicate that providing post-exposure prophylaxis for non-occupational exposures to all gay and bisexual men at high risk in Vancouver's West End would cost a minimum of $800,000.