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.
The full guideline is available in Appendix 1 (at www.cmaj.ca/ lookup/suppl/doi:10.1503/cmaj.170494/-/DC1).
This guideline is applicable to adults who are at risk for acquiring HIV infection through sexual activity or injection drug use, but may be of particular importance in populations where HIV incidence in Canada remains disproportionately concentrated. More than half of new infections (54.3%) occur in gay, bisexual and other men who have sex with men (MSM), in whom HIV risk is estimated to be 131 times higher than other men. (6) HIV incidence among people who inject drugs (PWID), people from HIV-endemic countries, and Indigenous people is estimated to be 59, 6.4 and 2.7 times higher than in other Canadians, respectively. (6) National data on HIV incidence among sex workers and their clients are scarce, perhaps in part because sex work is criminalized in Canada; as such, this guideline should be applied to these individuals based on the presence of other risk factors.
We adopted a client perspective, as our primary intended audience is clinicians working in primary care, infectious diseases, emergency medicine, nursing, pharmacy and related disciplines. In addition, policy-makers, community organizations and other stakeholders may find this guideline useful for informing policy and programming.
The guideline was developed by the Biomedical HIV Prevention Working Group of the CIHR Canadian HIV Trials Network, with funding from the Canadian Institutes of Health Research and inkind support from the CIHR Canadian HIV Trials Network. We followed the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) system, a rigorous and widely accepted methodology for the development of clinical practice guidelines (Box...