Prevention in Focus

Fall 2018 

Research Update: Canadian study shows changes in attitudes about treatment as prevention among HIV-positive and HIV-negative MSM

By Mallory Harrigan

Biomedical research demonstrating the benefits of taking HIV treatment to prevent HIV transmission (known as treatment as prevention, or TasP) has developed substantially in recent years. We are now able to say with confidence that an HIV-positive person who takes antiretroviral treatment (ART) and maintains an undetectable viral load cannot pass HIV to a sexual partner. This represents a major breakthrough in the field of HIV, both for its prevention implications and for its potential to reduce stigma faced by people living with HIV. However, when a health innovation like this emerges, it can take time for the information to reach the communities who would most benefit from it. Gay, bisexual and other men who have sex with men (MSM) represent over half of people living with HIV in Canada, so this community stands to benefit from using TasP as a highly effective strategy for HIV prevention.

The study

A study called the Momentum Health Study looked at perceptions about TasP in a total of 774 MSM in Vancouver (556 were HIV negative or had an unknown HIV status, and 218 were HIV positive). The study tracked participants’ beliefs about TasP between 2012 and 2016. Research about TasP was accumulating during this time period, with two major studies releasing their final results in 2016.

In the Momentum study, men filled out the same survey up to seven times, at 6-month intervals. The survey asked respondents:

  • whether they had heard of TasP, and if they believed it was effective
  • demographic and lifestyle questions
  • questions about their sexual practices and substance use


Awareness and perceptions of TasP

Each time a participant filled out the survey, they were grouped into one of three classes based on their answers to a series of questions about TasP:

  • Unaware: They had not heard of TasP
  • Skeptical: They had heard of TasP but were not confident that it was effective
  • Believing: They believed that TasP was effective

At the beginning of the study, HIV-positive men were more aware of TasP compared to HIV-negative men. At their first time filling out the survey, 44% of HIV-positive men believed in TasP, 22% were skeptical that it was effective, and 33% were unaware of TasP. When HIV-negative men first filled out the survey, only 4% believed that TasP was effective, 23% were skeptical of TasP, and almost three quarters (74%) were unaware of TasP.

Changes over time

HIV-positive men’s perceptions of TasP remained relatively stable over time. Over the course of the study the proportion of HIV-positive men who believed in TasP increased slightly (from 44% to 53%), and the proportion who were unaware of TasP decreased slightly (from 33% to 29%), as did the proportion who were skeptical (from 22% to 18%). These changes were not statistically significant.

However, over the course of the study, perceptions about TasP among HIV-negative men changed quite dramatically. The proportion of HIV-negative men who believed in TasP increased significantly from 4% to 15%. The proportion of HIV-negative men who were skeptical about TasP increased from 23% to 52%, and the proportion who were unaware of TasP decreased from 74% to 33%.

Implications for service providers

Throughout the study, HIV-negative men were less believing in TasP compared to HIV-positive men, although HIV-negative men’s awareness steadily increased over the course of the study. The slower uptake of information among HIV-negative men suggests that it may be particularly effective to target these men for educational outreach relating to TasP. Increased awareness of TasP among HIV-negative men, the authors argue, would help to reduce HIV stigma and challenge the idea that people living with HIV are solely responsible for HIV prevention.

Many participants in this study – particularly HIV-negative men – were aware of TasP but questioned whether it was an effective strategy. This highlights that knowing about TasP does not necessary mean believing that it is effective. While it is certainly important to provide information about TasP to increase knowledge, those developing education campaigns might also explore strategies to increase confidence in TasP as a highly effective prevention strategy.


Card KG, Armstrong HL, Lachowsky NJ, et al. Belief in treatment as prevention and its relationship to HIV status and behavioral risk. Journal of Acquired Immune Deficiency Syndromes. 2018;77(1):8–16.

About the author(s)

Mallory Harrigan is CATIE's Knowledge Specialist, HIV Prevention. She has a Master's degree in Community Psychology from Wilfrid Laurier University.