A growing body of evidence tells us that oral pre-exposure prophylaxis (PrEP) is a highly effective strategy for reducing the risk of HIV transmission when used consistently and correctly. In February 2016, Health Canada approved the daily use of the drug Truvada as PrEP, in combination with safer sex practices, to reduce the risk of sexual HIV transmission for people at high risk of HIV infection. This approval was a necessary step towards increasing access to PrEP in Canada. However, for PrEP to have an impact on preventing new HIV infections, it needs to be available to and used by people who are at high risk of getting HIV. Canadian service providers have a role to play in facilitating awareness, access and use of this HIV prevention tool.
This article will review research related to PrEP in the Canadian context and what we know about awareness, acceptability and uptake of PrEP in Canada.
PrEP Effectiveness Research and Canadian Contributions
The effectiveness of daily oral PrEP has been demonstrated in multiple randomized controlled trials (RCTs) in countries other than Canada. Overall, the effectiveness of daily PrEP at reducing the risk of sexual HIV transmission ranged from zero to 86% in studies conducted among gay men and other men who have sex with men (MSM) and heterosexual men and women.1,2,3,4,5,6 The reason for this wide disparity is that not everyone was taking PrEP consistently. To demonstrate the importance of adherence, additional analyses in these trials looked at drug levels in the blood as a measure of who was taking PrEP consistently and who was not. These analyses found that daily PrEP reduced the risk of sexual HIV transmission by between 85% and 92% among participants who took the drug consistently compared to those who did not. One RCT has evaluated the use of daily oral tenofovir as PrEP in people who inject drugs. This study found that PrEP reduced the risk of HIV transmission by 49% overall, and by 84% among people who took PrEP consistently compared to those who did not.7,8
Canada has contributed to our knowledge of the rare circumstances in which HIV can be transmitted even when PrEP is used consistently and correctly. There have been two well-documented cases of HIV infection in people taking daily PrEP.9,10 The first reported case was a gay man from Toronto, who was adherent to PrEP for two years but became infected with a strain of HIV that was resistant to multiple antiretroviral drugs, including both of the drugs in Truvada.9 Although this type of resistance is rare, this case has been an important addition to international PrEP research because it highlights that transmission can occur even when PrEP is being used consistently and correctly.
Canada has also contributed to our knowledge of intermittent oral PrEP, taken "on-demand" for sexual HIV exposures. This strategy involves taking two pills before sex followed by one pill every day until two days after the last sexual event. The IPERGAY trial, which demonstrated the effectiveness of intermittent PrEP, included 400 gay men and other MSM in France and Montreal.11 The Montreal site enrolled 43 participants (11% of the total sample). The first phase of IPERGAY was a randomized trial, which found an 86% reduced risk of HIV infection among gay men taking intermittent PrEP compared to men taking a placebo (two participants in the PrEP group became infected compared to 14 in the placebo group). Adherence analyses showed that, overall, men in this study were having sex frequently, and taking an average of four pills per week. The trial continued as an open-label extension with all participants offered intermittent PrEP, and one further HIV infection occurred among 362 participants in the open-label extension.12 None of the three participants who became infected over the course of the entire study had PrEP drugs detected in their blood, which means they were not actually taking PrEP consistently. The results from this study are important because they demonstrate that an intermittent PrEP strategy can be considered for use by MSM to reduce the risk of HIV transmission.
Are Priority Populations Aware of PrEP?
Awareness of PrEP among high-risk communities is varied.13,14,15,16,17,18 Increasing PrEP uptake among those at highest risk of HIV transmission requires that they know about it and want to use it. The majority of Canadian research about awareness and willingness to use PrEP has been conducted in gay men and other MSM, with few studies looking at other at-risk populations.
Research has found varying levels of PrEP awareness among MSM in Canada,13 but awareness appears to be increasing over time. For example, surveys conducted among MSM presenting for anonymous HIV testing in Toronto showed that awareness of PrEP has been steadily increasing. The proportion of MSM aware of PrEP in this population has increased from 14% in 201014 to 72% in 2015.15 However, levels of awareness seem to vary across the country. Research conducted in Vancouver from 2012 to 2014 found that only 21% of HIV-negative MSM were aware of PrEP,16 and a recent survey of MSM in Ottawa17 found that 53% knew about it.
Other priority populations may be much less aware of PrEP as an HIV prevention option. In a 2013 survey of people who inject drugs in Vancouver, only 3% knew about PrEP.18 Similarly, service providers working with African, Caribbean and Black (ACB) communities have reported low levels of PrEP awareness in their communities.19 Some attribute this to stigma around HIV leading to limited knowledge about HIV prevention in general in ACB communities.19
Perceived Risk of HIV and Willingness to Take PrEP May Impact Uptake Among at-Risk Populations
Despite growing awareness of PrEP among MSM in particular, increasing PrEP uptake among high-risk MSM may be challenging if they do not see themselves at high risk of HIV transmission or if they are unwilling to use it.
A study among MSM presenting for HIV testing at a Toronto sexual health clinic15 tried to identify the proportion of "optimal" MSM PrEP candidates. This study defined an "optimal" candidate as one who:
- is at objectively high risk for HIV based on self-reported risk behaviours (using an HIV-risk screening tool)
- perceives themselves to be at moderate-to-high risk, and
- is willing to use PrEP.
Between November 2014 and April 2015, 64% of 420 MSM were found to be at objectively high risk, 53% were willing to use PrEP, and 27% perceived they were at moderate to high risk of acquiring HIV. Only 16% were determined to be "optimal" PrEP candidates.
This study shows that increasing the uptake of PrEP among high-risk MSM may be challenging because many MSM either do not think they are at high risk of HIV transmission or are unwilling to take PrEP. Among men who were assessed to be at high risk for HIV (those likely to benefit from PrEP), 68% did not perceive themselves to be at high risk, and 40% said they were not willing to use PrEP.
Encouragingly, Canadian research suggests that MSM with a higher risk of HIV transmission may be more willing to use PrEP.15,20,21 Another Toronto study of HIV-negative MSM, surveyed between September 2010 and June 2012, found that 55% were willing to take PrEP. Willingness to use PrEP was associated with sexual risk behaviours, such as condomless anal sex with casual partners.20 A study in Montreal found that over half of MSM presenting for rapid HIV testing at a Montreal clinic between July 2012 and November 2013 were interested in taking PrEP. In this study, willingness to take PrEP was associated with high-risk behaviours, such as having more than 10 sex partners in the previous three months.21
A 2013 survey of HIV-negative people who inject drugs in Vancouver found that only one-third were willing to use PrEP if it were made available.18 Willingness to use PrEP in this population was associated with increased risk, such as requiring help injecting, engaging in sex work, and reporting multiple sex partners.
Canadian research has identified concerns that may lower willingness to take PrEP. For MSM this includes concerns about possible drug side effects, cost, adherence to daily pill-taking, lack of a family physician, or discomfort talking to a medical provider about sexual health.13,15,20 Research with people who inject drugs has identified concerns about PrEP side effects.18