With rising rates of HIV infection among patients, health care workers (HCWs) are increasingly at risk of contracting HIV through, for example, needlestick injuries. There are two prophylaxis options, which have different implications for both cost and cost-effectiveness. These are AZT prophylaxis and triple-combination therapy prophylaxis.
AZT prophylaxis involves taking 1000mg per day for four weeks after exposure. At US$ 15/day, the total cost is US$ 420. In addition, at least two HIV tests would be required - one to establish the patient’s HIV status and one to test the HCW’s status after prophylaxis. Counselling may also be considered necessary, and this will incur additional costs.
It has been estimated that there is a 0.3% risk of seroconversion after exposure, although study estimates range from 0 to 1.82% (Allen et al 1992). It has also been recently estimated that prophylaxis reduces this risk by 80% (MMWR June 7, 1996 p468) i.e. to 0.06%. Assuming a 0.3% risk of sero-conversion, this means that for every 10 000 health workers who are exposed to HIV but not given prophylaxis, 30 will be infected. With prophylaxis, for every 10 000 health workers exposed to HIV and given prophylaxis, 6 will be infected. Thus for every 10 000 health workers given prophylaxis, 24 infections will be prevented. The cost per prevented infection will be US$ 175 000
[6]. This figure suggests that prophylaxis may only be cost-effective in high-income countries. Moreover, cost-effectiveness in terms of years of life prevented will be further affected by the frequency with which HCWs are exposed to HIV infection: the more the exposures, the higher the chance that a given HCW will become infected and the lower the likely cost-effectiveness of prophylaxis.Prophylaxis with triple-combination therapy consists of 200mg of AZT three times a day, 150mg of lamivudine twice a day, and 800mg of indinavir three times a day (MMWR June 7 1996 p471) for four weeks. The cost of this regimen is US$26.4 per day, and US$792 for one month. If it is assumed that this regimen would be 100% effective, the cost would be US$264 000 per infection averted, making it less cost-effective than AZT prophylaxis.
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