STBBI prevention guide: Biomedical prevention

Last partial content update: November 2025

This page was created in November 2025.

Content about vaccination and HIV pre- and post-exposure prophylaxis (HIV PrEP and HIV PEP) was moved from the STBBI management page. The linked resources were updated.

Information about doxycycline for the prevention of chlamydia, gonorrhea and syphilis was incorporated.

This information is captured in the table of updates to the guides.

On this page

• Vaccination
• Prophylactic antiretroviral medications to prevent HIV
  • HIV PrEP
  • HIV PEP
• Prophylactic doxycycline to prevent chlamydia, gonorrhea and syphilis
  • Doxy-PEP
  • Doxy-PrEP
• References

Vaccination

Offer vaccination for hepatitis A virus (HAV), hepatitis B virus (HBV), human papillomavirus (HPV), and monkeypox virus (MPXV) to people at risk of these infections as per the Canadian Immunization Guide.

Refer to provincial or territorial vaccination schedules for more information:

• Vaccination schedule for infants and children
• Vaccination schedule for adults

Prophylactic antiretroviral medications to prevent HIV

The use of antiretroviral medications as part of a comprehensive approach to HIV prevention is an evolving area, with new research and evidence emerging. Consult Canadian, provincial or territorial guidelines for information about indications for HIV pre- and post-exposure prophylaxis (HIV PrEP and HIV PEP respectively), recommended baseline and follow-up testing, and prescribing information. Consult the relevant drug formulary regarding coverage.

HIV PrEP

HIV PrEP is the use of antiretroviral medication by people who are HIV negative - but at high risk of exposure to HIV – to prevent HIV infection^{Footnote 1}. Taking antiretroviral medication before exposure interrupts the virus's ability to copy itself in the body and prevents it from establishing an infection. The consistent and correct use of HIV PrEP is a highly effective strategy for HIV prevention.

Offer HIV PrEP to individuals at high risk for HIV infection as part of a combination prevention strategy which includes regular STBBI screening as well as ongoing counselling on adherence and risk reduction.

HIV PEP

HIV PEP is the use of antiretroviral medication by people who are HIV negative to lower the risk of HIV acquisition following a high-risk exposure. HIV PEP should be initiated as soon as possible, within 72 hours after an exposure. Adherence is essential for maximizing effectiveness^{Footnote 1}.

Baseline HIV status should be determined when HIV PEP is being considered.

HIV PEP is not intended for people with ongoing exposures to HIV and should not replace the use of other highly effective prevention strategies such as condoms and HIV PrEP^{Footnote 1}.

Prophylactic doxycycline to prevent chlamydia, gonorrhea and syphilis

Evidence is emerging regarding use of the antibiotic doxycycline as pre- or post-exposure prophylaxis to prevent chlamydia, gonorrhea and syphilis infections.

Published clinical studies to date have largely focused on doxycycline post-exposure prophylaxis (Doxy-PEP), with most of these studies conducted among cisgender gay, bisexual and other men who have sex with men (GBMSM) and transgender women (TGW)^{Footnote 2Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7}. Among cisgender GBMSM and TGW, Doxy-PEP prevented chlamydia and syphilis, and, in some cases, gonorrhea, infections over 12-to-18 months^{Footnote 2Footnote 3Footnote 4Footnote 6Footnote 7}. These findings indicate that Doxy-PEP has the potential to reduce disproportionate rates of infections.

In considering the role of prophylactic antibiotics, it is important to note that the prevention and management of chlamydia, gonorrhea and syphilis occur within a broader context of antimicrobial use (AMU) and antimicrobial resistance (AMR).

Drug-resistant pathogens, including pathogens with tetracycline co-resistance, disproportionately affect GBMSM (e.g., multidrug-resistant [MDR] Neisseria gonorrheae, extensively drug-resistant [XDR] Shigella)^{Footnote 8Footnote 9Footnote 10}. The use of tetracycline-class antimicrobials, such as doxycycline, creates AMR selection pressure, and widespread use of Doxy-PEP may result in the acceleration of AMR and MDR in bacterial STI and other organisms (e.g., Staphylococcus aureus)^{Footnote 4Footnote 7Footnote 11}.

In Canada, rates of tetracycline resistance in gonorrhea are very high. In 2023, 47.3% of gonorrhea cases included in the Enhanced Surveillance of Antimicrobial Resistant Gonorrhea (ESAG) system had tetracycline resistance. Among gonorrhea cases identified as GBMSM, 56.7% had tetracycline resistance^{Footnote 9}. In this context, the benefit of Doxy-PEP for preventing gonorrhea is expected to be lower than for chlamydia and syphilis. The durability of any benefit will be highly dependent on the evolution of AMR.

Doxy-PEP

Doxycycline pre-exposure prophylaxis (Doxy-PEP) is the use of a single 200 mg dose of oral doxycycline following condomless sex to prevent chlamydia, syphilis, and possibly gonorrhea.

Recommendations on the use of Doxy-PEP for bacterial STI prevention

Doxy-PEP for cisgender GBMSM and TGW

Consider offering Doxy-PEP (200 mg orally, taken within 72 hours of exposure) to cisgender GBMSM and TGW at increased risk of bacterial STI as a component of comprehensive STBBI services to reduce the risk of syphilis, chlamydia and possibly gonorrhea^{Footnote 12}.

Notes:

• There is no consensus definition for "increased risk" at this time. Examples of behaviours that can increase an individual's risk of bacterial STI include elements such as:
  • recent prior bacterial STI;
  • 10 or more partners in the last 6 months or condomless sex with multiple partners;
  • engaging in chemsex (using stimulants during sex e.g. crystal methamphetamine); and
  • engaging in group sex.
• Users are advised to take no more than 1 dose (200 mg) in a 24-hour period.
• To minimize antimicrobial use, if a Doxy-PEP user has multiple sexual partners during 3 consecutive days (e.g. a weekend), a single dose of Doxy-PEP at the end of the 72-hour period (e.g. on Monday morning after the weekend) should adequately cover their STI risk.
• The use of Doxy-PEP should be reassessed every three to six months as an individual's risk may change over time.
• Clinicians should follow existing STI screening recommendations. The optimal frequency of STI screening for individuals taking Doxy-PEP is not known. The NAC-STBBI suggests targeted "opt-out" syphilis, chlamydia and gonorrhea screening as frequently as every 3 months when serving population groups and/or communities experiencing high prevalence of syphilis (and other STBBI), including GBMSM. Refer to the Chlamydia (including LGV), Gonorrhea, and Syphilis guides for additional information.
• Given AMR concerns for gonorrhea, when testing for gonorrhea, there are several scenarios when specimens should be collected for both culture and NAAT, including for individuals with symptoms and when assessing gonorrhea contacts. For individuals who were diagnosed with gonorrhea using NAAT specimens only, collect a specimen for culture prior to administering treatment, as long as doing so does not delay treatment. Routine tetracycline susceptibility testing by laboratories can enable monitoring tetracycline resistance in gonorrhea. Refer to the Gonorrhea guide for additional information.
• Use of doxycycline as prophylaxis against bacterial sexually transmitted infections (STI) is an off-label indication.

Counselling on Doxy-PEP risks for shared decision-making

To inform shared clinical decision-making about Doxy-PEP use, discuss personal, community (e.g., GBMSM) and population-level risks of AMR with individuals considering this intervention^{Footnote 12}.

Notes:

Clinicians are advised to discuss the following elements with individuals taking Doxy-PEP:

• Globally, high antimicrobial use among GBMSM has been linked to a disproportionate burden of emergent and circulating AMR pathogens. Extra consideration should be given to prudent use of antimicrobials with this population.
• Existing evidence raises concerns about the potential of Doxy-PEP to contribute to the acceleration of tetracycline resistance in gonorrhea and indicates that any initial benefit for its prevention may not be sustained over the long term.
• To date, tetracycline resistance in chlamydia and syphilis have not been stably documented in humans, although syphilis has developed AMR to other antibiotic classes.
• Doxy-PEP use may contribute to the development of AMR in other organisms e.g., Staphlococcus aureus.
• Only doxycycline (as Doxy-PEP) has been proven effective for the prevention of bacterial STI; the use of other classes of antibiotics for STI prophylaxis is not recommended.

Doxy-PrEP

There are several studies underway to evaluate the effectiveness and safety of the use of daily oral doxycycline pre-exposure prophylaxis (Doxy-PrEP) to prevent bacterial STI. PHAC and the NAC-STBBI are monitoring the situation closely and will develop recommendations on the use of Doxy-PrEP as appropriate.

Additional resources

• Pan-Canadian Action Plan on Antimicrobial Resistance
• Enhanced Surveillance of Antimicrobial-Resistant Gonorrhea System (ESAG) dashboard