At press time, Health Canada has not approved the use of any anti-HIV drug for the purposes of PrEP. Currently, the American Food and Drug Administration (FDA) is considering the approval of Truvada as PrEP. Some public health departments in California are conducting observational studies of PrEP among men who have sex with men (MSM), and in France a trial of intermittent PrEP among MSM is underway. It is possible that such observational or other types of PrEP studies could come to Canada or that Truvada as PrEP may be approved by Health Canada one day. Before PrEP becomes licensed, it is important to find out what sexually active gay and bisexual men know about it and whether they are currently using it. This latter possibility is occurring in some American cities, according to anecdotal reports.
Leading infectious disease researcher Darrell Tan led a team that surveyed sexually active men undergoing HIV testing at a sexual health clinic in downtown Toronto about their sexual behaviour and PrEP. Of the 256 men surveyed, nearly 12% knew about PrEP, particularly men who have sex with men. None of the men disclosed any use of PrEP and many were interested in the future use of PrEP, should it be licensed in Canada.
The study was done in cooperation with the staff at Toronto's Hassle Free Clinic. Participants were all undergoing rapid HIV testing and they all had negative results.
In total, 256 men completed the survey. Participants were either men who had sex with men (MSM) or men who had sex with women (MSW). About 90% of the men were between the ages of 20 and 50 years.
Results -- Sexual Behaviours
More MSM (39%) had five or more sexual partners within the past six months compared to MSW (20%).
Of all the common sexual behaviours, unprotected anal sex carries the greatest risk for HIV transmission, so the research team enquired about this.
- When asked if they had unprotected anal sex in the past six months, 53% of MSM disclosed that they did. Among MSW, the figure was 21%.
- Roughly 27% of MSM and 12% of MSW disclosed that in the past six months they engaged in unprotected anal intercourse while under the influence of alcohol.
- About 10% of MSM and 5% of MSW disclosed that in the past six months they had unprotected anal intercourse under the influence of both alcohol and drugs.
Questioned About PrEP
About 14% of MSM and 5% of MSW reported that they had heard of PrEP. This difference was statistically significant.
When the men were asked if they would be willing to use PrEP if it was "proven safe and effective," many men, particularly MSM, were willing to do so.
None of the men in the study had used PrEP.
A similar recent study in New York City that recruited 554 MSM from two of the city's bathhouses found that 60% of MSM had unprotected anal sex in the past three months. About 36% of participants were aware of PEP or PrEP. Both the Toronto and New York City studies show that there is an urgent need to intensify HIV prevention activities.
The Toronto researchers stated: "Determining whether, where, when and how to optimally roll out PrEP will require a multi-stakeholder process to ensure [that] optimal strategies for financing, administering and monitoring this promising new HIV prevention strategy are developed."
Important Facts About Using PrEP
The results of the iPrEx study show that when used for about one year, Truvada can provide partial protection against HIV infection, at least among high-risk MSM. However, before embarking on widespread use of Truvada as PrEP, there are several issues to consider.
Condoms are still needed
Truvada is only modestly effective in preventing HIV infection and cannot replace safer sex. Dr. Kevin Fenton, director of the National Center for HIV/AIDS at the American Centers for Disease Control and Prevention (CDC), says that the iPrEx data are "encouraging," however, he adds, "this is not the time for gay men to throw away their condoms."
Resistance and reduced treatment options
People using PrEP require frequent HIV testing. It is very important that people considering PrEP are not infected with HIV because of the risk of developing drug resistance. More than 25% of people living with HIV in Canada are not aware of their HIV status. Furthermore, the risk of resistance may be greatest during acute HIV infection, when conventional HIV tests cannot detect infection.
Hepatitis B virus
Hepatitis B virus (HBV) can be sexually transmitted, particularly among MSM. Men who are interested in using PrEP need to first be screened for HBV infection; if found negative and unvaccinated, they should be given the vaccine to protect them from this virus. Truvada also possesses anti-HBV activity. As a result, it can help place chronic HBV infection into remission. Among people with chronic HBV, suddenly stopping treatment, such as Truvada, can cause HBV to come out of remission and affect a person's health.
Effectiveness of PrEP in other populations
The iPrEx study involved MSM who were at high risk for HIV infection. The primary mode of exposure to HIV was through rectal tissue during unprotected receptive anal intercourse. According to the investigators, this study does not provide any information about effectiveness or safety of PrEP for vaginal, penile or intravenous exposure to HIV. Further studies are needed to determine if PrEP has any effect in reducing HIV transmission from heterosexual vaginal sex, intravenous drug use or insertive anal sex.
Safety and use in the real world
We don't know how willing gay and bisexual men will be to take PrEP over the long term. We know from people living with HIV that taking anti-HIV drugs on a regular basis is a challenge and can lead to long-term side effects that are difficult to manage. Truvada can affect the health of the kidneys and bones in HIV-positive people. Commonly used over-the-counter drugs such as acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) can also affect kidney health.
PrEP must be provided within the context of a comprehensive prevention program. The iPrEx trial participants were frequently monitored for sexually transmitted infections (STIs), HIV and drug toxicity. They were also offered regular HIV risk counseling and adherence support. In the "real" world outside the clinical trial, for PrEP to work, people on PrEP will need close medical supervision, regular safer-sex counselling, and frequent testing for HIV and STIs. Some HIV-negative men may feel that this level of bio-medical intervention is too intrusive.
PrEP and risk behaviour
Another concern is that some people may feel a false sense of security when using PrEP and may decide to engage in more risky activities. If people using PrEP have sex with more partners, use condoms less often, or share needles more frequently, their overall risk for HIV infection (and other STIs) may increase because PrEP does not provide complete protection.
Currently, PrEP is a very expensive intervention. A one-month supply of 30 Truvada pills costs at least $800 in Canada or the U.S. -- $27 per day.
Unsupervised use of PrEP
PrEP involves taking anti-HIV drugs. These medications must be prescribed and monitored by a doctor, who can provide them in a safe and informed way. Some people may be tempted to experiment with drugs obtained from other sources -- from a friend, people at parties, or over the Internet. This could be harmful. Incorrect use of anti-HIV drugs can cause HIV drug resistance. It might also cause serious, even life-threatening, reactions in some people. Anti-HIV drugs can interact with prescription drugs, recreational drugs and other substances. These interactions can be harmful, even when there are no symptoms.
CATIE Fact Sheet on Pre-exposure prophylaxis (PrEP)
CDC Statement on Results of iPrEx Trial
CATIE Fact Sheet on Truvada
Grant RM, Lama JR, Anderson PL, et al. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. New England Journal of Medicine. 2010 Dec 30;363(27):2587-99.
Michael NL. Oral preexposure prophylaxis for HIV -- another arrow in the quiver. New England Journal of Medicine. 2010 Dec 30;363(27):2663-5
McNeil DG Jr. Daily pill lowers AIDS risk, study finds. New York Times. 23 November 2010.
Leonardi M, Lee E, Tan DH. Awareness of, usage of and willingness to use HIV pre-exposure prophylaxis among men in downtown Toronto, Canada. International Journal of STD and AIDS. 2011 Dec;22(12):738-41.