HIV factsheet: Biomedical prevention of HIV – PrEP and PEP

PrEP and PEP
Question Pre-exposure prophylaxis (PrEP) Post-exposure prophylaxis (PEP)
What are PrEP and PEP? PrEP involves taking a combination of medications to reduce the risk of acquiring HIV infection. It can be taken by HIV-negative individuals at high risk of infection. When taken as prescribed, the medication reduces the risk of acquiring sexually transmitted HIV by more than 90%. If an individual acquires HIV infection, PrEP must be discontinued immediately. PEP is used to help prevent the acquisition of HIV infection by individuals who may have been recently exposed to HIV. PEP can reduce the risk of HIV infection by more than 80%, when used as prescribed.
When is it taken? PrEP is taken once a day, on an ongoing basis, in advance of high-risk activity. PrEP is less effective if the prescribed dosing schedule is not followed. PEP is effective when taken within 72 hours of suspected high-risk exposure to HIV. It involves antiretroviral medications taken once daily for 4 weeks (28 days).
Who should be considered for PrEP and PEP? Individuals at high risk of HIV infection:
  • engages in condomless sexual activity with an HIV-positive partner who is not on treatment or whose viral loadFootnote * is ≥ 200 copies/ml
  • engages in condomless sexual activity with a partner whose HIV status is unknown
  • engages in sexual activity that involves:
    • no or inconsistent condom use
    • exchange of sex for drugs or money
    • use of illicit drugs or alcohol dependence
  • shared drug use equipment
  • have a diagnosis of sexually transmitted infections (STI)
  • prison experience

In addition, PrEP should be considered for individuals who have taken PEP (i.e., who are at ongoing, high risk of infection).

PEP should be considered for individuals:
  • who have had a high-risk exposure to HIV in the workplace (e.g., health care setting) or
  • who have had a high-risk exposure to HIV outside of the workplace (e.g., condomless sex with an HIV-positive partner who is not on treatment or whose viral loadFootnote * is ≥ 200 copies/ml, sexual assault, etc.)

Other considerations

Strict adherence to the prescribed regimen is essential for the efficacy of PrEP and PEP. Regular HIV and STI testing (i.e., at least once every 3 months) is necessary for patients taking PrEP.

PEP complements, but doesn't replace, other HIV prevention methods such as condoms or PrEP.

Consult with your provincial/territorial HIV programs for more information on coverage of PrEP and PEP through provincial/territorial drug formularies.

For more prevention and treatment information, consult an infectious disease specialist or physician with experience in the management of HIV.

Additional resources

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