Canadian Guidelines on HIV Pre-Exposure Prophylaxis and nonoccupational Post-Exposure Prophylaxis

Introduction

New HIV infections occur every year in Canada,1 highlighting the need for integrated prevention programs. Pre-exposure prophylaxis (PrEP) and nonoccupational postexposure prophylaxis (nPEP) are two important strategies for preventing HIV that should be considered standard of care and implemented as components of a comprehensive response to the epidemic. Pre-exposure prophylaxis is the use of certain antiretroviral medications by HIV-uninfected persons who are at high, ongoing risk of HIV acquisition, beginning before and continuing after potential HIV exposures. Postexposure prophylaxis (PEP) involves 28 days of antiretroviral medications immediately after a specific HIV exposure, and is “nonoccupational” (nPEP) when used after sexual and injection drug use exposures, rather than accidental exposures that occur in work contexts (e.g., health care). The risk of HIV acquisition from an exposure depends on the likelihood the source has transmissible HIV infection (Table 1), 2–4 which we categorize as substantial, low but nonzero, and negligible or none, and the biological risk of HIV transmission based on the exposure type, which we categorize as high, medium or low (Table 2).5 We distinguish between three categories for the likelihood that a person has transmissible HIV infection: substantial, low but nonzero, and negligible or none. The categories for the likelihood that a source has transmissible HIV infection depend on the person’s HIV treatment status if known to be HIV positive, or on the probability of the person being HIV positive if HIV status is unknown.