Canadian guideline on HIV pre-exposure prophylaxis and nonoccupational postexposure prophylaxis

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Led by Treatment & Prevention Think Tank Co-lead Dr. Darrell Tan, this document from the CTN+ Biomedical HIV Prevention Working Group provides a clinical update on PrEP and nPEP as HIV prevention strategies.

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Key Points

• Pre-exposure prophylaxis (PrEP) involving daily tenofovir disoproxil fumarate/emtricitabine 300/200 mg, taken orally, is a highly effective strategy for reducing the risk of HIV acquisition in adults who are at high, ongoing risk of infection.

• In gay, bisexual and other men who have sex with men with frequent exposures, an on-demand regimen may also be considered.
• Nonoccupational postexposure prophylaxis (nPEP) involving 28 days of antiretroviral medications is an effective strategy for reducing the risk of HIV acquisition from a recent (within 72 h) incident of moderate or high-risk exposure to HIV.
• PrEP and nPEP should be part of a combination prevention strategy that includes behavioural interventions, such as condoms and counselling on risk reduction.

Summary

New HIV infections occur every year in Canada, 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, 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. We distinguish between three categories for the likelihood that a person has transmissible HIV infection: substantial, low but non-zero, 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.