A four-week course of antiretroviral drugs to prevent HIV infection begun within 72 hours of exposure to the virus does not guarantee remaining HIV-free, according to researchers at the University of California, San Francisco. They followed 702 people given postexposure prophylaxis after nonoccupational exposures to HIV, and at a 12-week follow-up after treatment seven people were shown to have contracted HIV. Three of the seven had no other exposures to HIV and were determined to have seroconverted despite taking the anti-HIV drugs; it was unclear whether the remaining four had been exposed to HIV at other times.
'PEP is not completely effective in preventing HIV infection following nonoccupational exposure. Therefore, primary prevention remains essential,' the researches wrote in the journal Clinical Infectious Diseases.