Pre-exposure and post-exposure prophylaxis for sexual exposure to sexually transmitted infections

Note: This page provides an overview and resources for PrEP and PEP for sexual exposure to STIs. For information on non-sexual exposures to blood borne pathogens (HIV, hepatitis B and C), refer to OPH’s Assessment and management of non-sexual exposure to blood borne pathogens.

Key Messages

  • Safe and effective regimens are now available for pre-exposure prophylaxis (PrEP) of HIV, and post-exposure prophylaxis (PEP) of HIV and bacterial STIs.
  • It is appropriate to prescribe HIV PrEP to all adult and adolescent patients who request it, and clinicians are encouraged to assess HIV risk during routine health visits to identify additional people who would benefit from this intervention.
  • Clinicians are encouraged to normalize discussions of PrEP and PEP as part of routine sexual health assessments, using affirming and culturally safe approaches with gay, bisexual, and other men who have sex with men; people who use injection drugs; Indigenous peoples; African, Caribbean, and Black communities; and transgender women.
 Introduction
  • Rates of HIV and bacterial STIs disproportionally impact several populations (See Epidemiology section below for additional details).
  • Biomedical prevention is part of a comprehensive strategy for reducing the incidence of HIV and STIs in Canada, including HIV PrEP/PEP with antiretroviral therapy for reducing the risk of HIV infection and doxycycline PEP (doxy-PEP) for reducing the risk of bacterial STIs.
  • Canadian guidelines for HIV PrEP/PEP and doxy-PEP were released in 2025 (See Resources for Physicians and Nurse Practitioners below). A Health Canada review of doxy-PrEP for bacterial STIs is forthcoming.
  • Health professionals should be aware of recommendations regarding HIV PrEP/PEP and doxy-PEP, and normalize discussions about PrEP/PEP as part of assessing sexual health.
  • All sexually active adolescents and adults and those who use injection drugs should be counselled about HIV PrEP/PEP as part of a broad approach to preventing HIV transmission.
 Epidemiology
  • Local infection rates for HIV, chlamydia, gonorrhea, and syphilis can be reviewed on the Diseases of Public Health Significance in Ottawa dashboard.
  • Provincial epidemiology surveillance reports for sexually transmitted infections are prepared by Public Health Ontario.
  • Highlights of local and provincial trends as of February 2026 are as follows:
    • Rates of chlamydia, gonorrhea, syphilis, and HIV infections increased in Ottawa in 2022-2024 compared to previous years.
    • HIV infections remain disproportionately concentrated in key populations including gay, bisexual, and other men who have sex with men, people who use injection drugs, Indigenous peoples, and African, Caribbean, and Black communities.
    • Bacterial STIs, like syphilis and gonorrhea, disproportionally impact certain populations including gay, bisexual, and other men who have sex with men and transgender women.

 HIV pre-exposure prophylaxis (PrEP)
  • Canadian HIV PrEP guidance was updated in 2025: Canadian guideline on HIV pre- and postexposure prophylaxis: 2025 update (CMAJ).
  • HIV PrEP involves taking antiretroviral medication prior to, at the time of, and after high-risk exposures, and is therefore taken either routinely or on-demand when high-risk sexual exposures are anticipated.
  • HIV PrEP is recommended for individuals who participate in activities with increased risk of exposure to HIV. It should be offered to adults and adolescents who request HIV PrEP. Clinicians are also encouraged to assess HIV risk during routine health visits to identify additional people who may benefit from PrEP.
  • HIV PrEP should involve clinical evaluation and documentation of HIV seronegativity at the time of initiation and every 2-3 months thereafter, depending on the type of PrEP being prescribed. Additional screening for other STIs should be performed at these same clinical visits, alongside regimen-specific considerations as described in the 2025 Canadian guidelines for HIV PEP/PrEP.
  • Multiple safe and effective options are available for HIV PrEP, including oral and long-acting injectable therapies. Preferred regimens depend on patient factors, which should be elicited in a culturally sensitive and affirming manner, and are described in the 2025 Canadian guidelines for HIV PEP/PrEP. A summary of these from the Guidelines is as follows:
    • Daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) is the most widely evaluated regimen and has demonstrated excellent safety and efficacy (near 100%), and good acceptability.
    • Daily tenofovir alafenamide/emtricitabine (TAF/FTC) has been shown to be noninferior to TDF/FTC and may be preferred among those with renal disease or osteoporosis, though is not currently available in generic form and is therefore more costly, and is not listed on the Ontario Drug Benefits Formulary.
    • On-demand TDF/FTC PrEP may also be suitable for select populations, though decision-making should consider that it has not been evaluated as extensively as daily PrEP, and it is not approved by Health Canada for HIV PrEP (i.e., used off-label).
    • Long-acting injectable cabotegravir was approved by Health Canada in 2024 as HIV PrEP. It has shown superior efficacy over daily TDF/FTC and has high acceptability.

HIV post-exposure prophylaxis (PEP)
  • Canadian HIV PEP guidance was updated in 2025: Canadian guideline on HIV pre- and postexposure prophylaxis: 2025 update (CMAJ).
  • The risk of HIV acquisition depends on both the likelihood that the source has transmissible HIV infection and the risk of HIV transmission based on the type of exposure.
  • HIV PEP involves taking antiretroviral medication to prevent HIV infection after a moderate- or high-risk exposure to someone with a substantial risk of having transmissible HIV infection.
  • HIV PEP should be started as soon as possible, ideally within the first 24 hours, but can be started up to 72 hours after exposure. HIV PEP should not be initiated after 72 hours from exposure. HIV baseline testing is recommended but should not delay initiation of HIV PEP.
  • HIV PEP consists of a 28-day course of oral pills taken daily. Multiple safe and effective regimens are available, with preferred regimens of bictegravir/tenofovir alafenamide/emtricitabine (bictegravir/TAF/FTC) or dolutegravir plus tenofovir disoproxil fumarate/emtricitabine (dolutegravir plus TDF/FTC). Additional details are available in the 2025 Canadian guidelines for HIV PEP/PrEP.
  • HIV PEP can be initiated and managed in the community for most patients. Consider consultation to Infectious Disease (e.g., Module G at The Ottawa Hospital) for those who: are pregnant; have GFR < 30 ml/min if starting bictegravir/TAF/FTC; or have GFR <60 mL/min if starting dolutegravir plus TDF/FTC.
  • For individuals where HIV PEP is indicated but cost-prohibitive, please contact the Ottawa Public Health Sexual Health Clinic at 613-560-6099 to discuss options.
  • Health professionals should offer HIV PrEP for individuals who have received non-occupational HIV PEP and who are at ongoing risk of HIV exposure. PrEP can be initiated immediately after PEP use (i.e., on day 29) without needing any break of chemoprophylaxis. 
  • HIV PEP is not indicated if the source person is HIV-negative, is living with HIV on treatment with a very low viral load (i.e. less than 200 copies/mL measured every 4-6 months), or if the HIV status of the source person is unknown and they are from the general population.

Doxycycline post-exposure prophylaxis (doxy-PEP) for bacterial STIs
  • Recommendations on the use of doxycycline for post-exposure prophylaxis (doxy-PEP) were released by PHAC in 2025: Recommendations on the use of prophylactic doxycycline for the prevention of bacterial STI (chlamydia, gonorrhea, syphilis).
  • Doxy-PEP may reduce the risk of syphilis, chlamydia, and possibly gonorrhea.
  • Doxy-PEP may be offered to cisgender gay, bisexual and other men who have sex with men (gbMSM) and transgender women at increased risk of bacterial STI, such as those who have had a recent bacterial STI, those with 10 or more partners in the last 6 months or condomless sex with multiple partners, those engaging in “chemsex” (using stimulants during sex), and individuals engaging in group sex.
  • Doxy-PEP consists of a single 200 mg dose of doxycycline, taken orally, ideally within the first 24 hours but up to a maximum of 72 hours after an exposure. No more than one dose should be taken in a 24-hour period; if a doxy-PEP user has multiple sexual partners within a 2-3 day period, a single dose at the end of the 72-hour period can be considered to minimize antimicrobial use.
  • The benefits and risks of doxy-PEP should be discussed to inform shared clinical decision-making, including concerns for personal, community, and population-level risks of antimicrobial resistance (see Recommendation 2, Health Canada).
  • Routine STI testing and re-evaluation of ongoing doxy-PEP should be performed every 3 to 6 months.
 Patient Resources

Sexually transmitted infections (STIs)

HIV PrEP/PEP

  • OPH webpage with factsheet for AIDS and HIV. Overview of HIV with brief information on PrEP and PEP, Ottawa Public Health
  • The Sex You Want. Website on HIV including separate webpages for PrEP and PEP, tailored for Gay men, Gay Men’s Sexual Health Alliance
  • HIV Prevention Medications. Resource on HIV PrEP, PEP, and “PEP in Pocket” (PIP), tailored for cis and Trans women, Women & HIV/AIDS Initiative
  • CATIE resources on HIV PrEP (brochure, pocket card, and video) and HIV PEP (brochure, video), Canadian AIDS Treatment Information Exchange

Doxy-PEP for bacterial STIs
 Resources for Physicians and Nurse Practitioners

 

    

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