About The Study

Focusing on gay, bisexual, and other men who have sex with men (gbMSM), the Engage Study will report on the occurrence of HIV and other sexually transmitted and bloodborne infections and related drivers. Originally planned to take place over a shorter time period, this cohort was extended until 2023 and will follow participants from Montreal, Toronto and Vancouver. The study aims to 1) measure trends in and determinants of: the use of antiretroviral (ARV)-based HIV prevention, psychosocial-behavioural factors (e.g., experiences of discrimination, substance use, access to prevention and care services, etc.), condom-use, bacterial sexually transmitted infections (STIs), and HIV and 2) examine the relationships between ARV-based HIV prevention and various sexual health outcomes (e.g., occurrence of STIs).

The collected data will also be compared between cities (Toronto, Vancouver, and Montreal), allowing researchers to evaluate current HIV and STI prevention strategies and to identify gaps in care and the shortcomings of current programming.

About The Disease

Modern HIV prevention strategies come in many different forms. Biomedical technologies such as pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) for HIV-negative individuals, and Treatment as Prevention (TasP; screening, antiretroviral (ARV) treatment and care retention) for HIV-positive individuals, are successful in decreasing HIV transmission.; an important key population to focus on that benefit from these HIV prevention strategies. Other prevention approaches, such as educational and safer sex counselling programs, especially in conjunction with other strategies, are also effective. However, uptake and exposure to these programs may differ between cities and between different groups of people. While gbMSM represent a small minority of the Canadian population, they account for half of prevalent HIV cases and half of new HIV diagnoses in Canada. Therefore, an understanding of the evolving impact of ARV-based HIV prevention within this key population, in the context of other effective prevention approaches, is essential at this critical time.

Study Approach

CTN 300 will collect information on the factors that affect HIV risk behaviour, access to prevention and treatment programs, and other determinants of HIV, hepatitis C virus (HCV), and bacterial sexually transmitted infections (STIs), like syphilis and gonorrhea. Also, biological specimens will be collected and analyzed to report on HIV and STI occurrence.

Approximately 2000 HIV+ and HIV- participants are followed across the three cities. The Engage Study used a method called Respondent Driven Sampling (RDS) to recruit participants at baseline. It involved selecting initial set of participants from the gbMSM community members to invite others through their social networks. Each subsequent participant was also asked to invite others to continue the chain of recruitment.

In addition to the biological tests, questionnaires are administered to determine sexual risk taking behaviour, knowledge of and access to educational and biomedical HIV preventions programs, and other information. The data are collected every six months and will be compared across cities and time points.

If you would like more information on this clinical study, please refer to the principal investigator or visit www.engage-men.ca.

Eligibility Requirements


  • Gender-identify as a man, including men who identify on the trans-masculine spectrum
  • 16 years of age or older
  • Reported sexual activity with a man in the previous six months
  • At baseline: Received an RDS voucher for participation in the study, or was invited to be an initial “seed” participant
  • Ability to complete a computer-based questionnaire in English (each site) or French (in Montreal)
  • Ability to provide informed consent

Additional Information

If you would like more information on this study, please refer to the principal investigator or visit www.engage-men.ca.

Principal Investigators

Here’s who is leading this study.

Can’t find what you’re looking for? Email ctninfo@hivnet.ubc.ca.

Participating Sites

Here’s where this study is being conducted.