CDC to reconsider AZT in post-exposure guidelines

New data may change 6-year-old document

The Centers for Disease Control and Prevention in Atlanta will update guidelines on managing occupational exposure to HIV and reopen the issue of whether to recommend zidovudine (AZT) prophylaxis for health care workers, reports David M. Bell, MD, chief of the HIV infections branch in the CDC hospital infections program.

Data have accumulated on many fronts since the current guidelines were written in 1989 -- including some "weak" but "very interesting" findings suggesting AZT's efficacy as a post-exposure prophylaxis, Bell said at a recent meeting of the CDC Hospital Infection Control Practices Advisory Committee (HICPAC).1

The CDC essentially adopted a neutral position regarding AZT in current guidelines, saying there was insufficient information to recommend or discourage its use for health care workers following exposure to HIV-infected blood. As a result, AZT is now routinely offered to exposed health care workers at some hospitals, while others may not offer the drug due to the lack of data and guidance from the CDC.

In addition to revisiting the AZT question, more information is now available on a variety of other issues pertinent to occupational exposures -- including the biology and immunology of early HIV infection, duration of follow-up, new antiviral agents either licensed or in development, toxicity, and other data from studies in both animals and humans, Bell said. (See related story, this page.)

"It's now six years later, and it has become apparent that there is a lot of additional information that may or may not change the actual recommendations, but [AZT use] clearly needs to be looked at in an organized way," he told the committee. ". . . There is not much more information about [AZT] efficacy, but there is a little that we developed and presented at some conference meetings and are now further evaluating."

Unpublished study shows promising results

That information includes an unpublished case control study of HIV seroconversion in health care workers after percutaneous exposure to HIV-infected blood. The study included 31 health care workers infected by needlestick injuries and 679 who suffered needlesticks but did not seroconvert, Bell said. A statistically significant finding was that workers who did not receive AZT after exposure were more likely to seroconvert than those who did receive the drug. The study -- the first suggesting AZT efficacy as a post-exposure prophylaxis -- has been interpreted cautiously by CDC officials.

"[A] variable that had significance was post-exposure use of zidovudine by these health care workers," Bell said. "This is weak information because it is a retrospective evaluation. . . . It was not a placebo-controlled, randomized, double-blind [study] that we would like to have . . . [but] this is one piece of very interesting information that we are continuing to look at and I think will need to be pursued and possibly revisited in the PHS statement."

Other risk factors for occupational infection in the study -- that could be factored into updated guidelines for post-exposure management -- included the volume of blood involved in exposures and whether the source patient was in terminal stages of AIDS suggestive of high viral titer. The CDC is still considering how to update the document, and Bell gave no time line for the process, which likely would again involve participation by both the Food and Drug Administration and the National Institutes of Health.

"I think the whole idea of prophylaxis recommendations for people who get exposed needs to be constantly re-looked at until we get something that is adequate and appropriate," says Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases in Bethesda, MD. "[The CDC] has some data historically when you look at the rate of infection since the use of AZT -- it seems to have gone down. [But] you can't feel strongly about it if you don't have the data."


1. Centers for Disease Control and Prevention. Public Health Service statement on the management of occupational exposure to HIV virus, including considerations regarding zidovudine post-exposure use. MMWR 1990; 118:913-919. *