In reply
We appreciate the comments of Coutellier and colleagues, who point out that despite zidovudine therapy, human immunodeficiency virus (HIV) may still be transmitted to an exposed health care worker. This has happened on at least eight occasions,1-3 including the case cited by Coutellier et al.3 Anecdotal accounts of failures following the use of zidovudine for postexposure prophylaxis are of great concern, but provide only limited information on the efficacy of this approach. Without more rigorously collected data, it is difficult to draw any firm conclusions regarding the efficacy of zidovudine prophylaxis or the risk-benefit ratio of this therapy. More compelling are the results of two recent studies. A US Public Health Service study compared health care workers since 1988 in whom seroconversion occurred after percutaneous exposure to HIV-infected blood with similarly exposed health care workers in whom HIV infection did not develop.4 The preliminary findings