Doctors, nurses and other health care workers who are accidentally exposed to HIV-tainted blood should promptly receive antiretroviral therapy, according to new recommendations issued by the Public Health Service (PHS).
The recommendations reflect mounting evidence that post-exposure prophylaxis with anti-HIV drugs can reduce the risk for infection among health care workers exposed to HIV on the job, combined with a recognition that the type of exposure has a lot to do with the risk for infection," says NIAID's Steven M. Schnittman, M.D. Dr. Schnittman was part of the PHS panel that formulated the new guidelines, which were published in the June 22, 1996 issue of Morbidity and Mortality Weekly Report.
A recent study by the Centers for Disease Control and Prevention (CDC) provided the basis for the panel's recommendations. The study found that health care workers treated with zidovudine (AZT) after accidental HIV exposure were 79 percent less likely to become infected than untreated workers (see Morbidity and Mortality Weekly Report, Dec. 22, 1995). The greatest risk for infection was associated with exposures involving deep skin punctures with hollow needles containing blood from late-stage AIDS patients. Exposures involving solid needles from patients with asymptomatic HIV infection carried the lowest risk.
The panel found support for their recommendations in an NIAID-funded study (ACTG 076) that showed that giving AZT to HIV-infected pregnant women and their infants reduced mother-to-infant HIV transmission by 67 percent (see The New England Journal of Medicine, Nov. 2, 1994).
The reduction of viral load by AZT in the mother is not the only determinant of prevention of maternal transmission of the virus," says Dr. Schnittman. "We don't know for sure, but there may be an element of post-exposure prophylaxis within the neonate. The presence of AZT in the newborns blood may prevent HIV from establishing and propagating infection."
Dr. Schnittman adds that the recent availability of new anti-HIV drugs, protease inhibitors in particular, increases hope for more effective post-exposure prophylaxis. "Now that we have additional therapies that can dramatically lower the amount of HIV in the blood, the concept of trying to prevent the replication of any transmitted virus by administering combinations of antiretroviral drugs is even more attractive."
The recommendations specify two- or three-drug treatment regimens, depending on the degree of risk associated with the exposure (see chart). If possible, treatment should begin within one to two hours of exposure, although the interval after which post-exposure prophylaxis is not effective has not been defined. The panel noted that the optimal duration of treatment also is unknown, but recommended that therapy be administered for four weeks, if tolerated.