Does PrEP work?

Yes, PrEP works! Research consistently shows PrEP, when taken as prescribed, significantly reduces the likelihood of acquiring HIV for cisgender men, and women who are transgender or cisgender. Unfortunately, there hasn't been enough research specifically about how PrEP works for transgender men, non-binary folks, or Two-Spirit people. PrEP research has focused on cisgender gay men and other men who have sex with men, transgender women, and cisgender men and women who are heterosexual and/or use injection drugs.

So far, research has only been done with people over the age of 18, so we do not know how PrEP works for younger youth. How much of a difference PrEP makes on our HIV risk varies greatly based on our exposure to HIV and how closely we are able to follow the prescription. If we are using PrEP, it is important to follow our doctor's instructions about how to use it. 

Studies have shown that PrEP reduces the risk of HIV acquisition between 74% and 92% among individuals who take the medication as prescribed. In these studies, research participants were also given access to safer sex counselling, STI testing and treatment, and condoms. The research participants reported a range of sexual acts and relationships, including having multiple partners, anal sex, and vaginal sex. PrEP does not prevent other STIs such as chlamydia, gonorrhea or syphilis.

PrEP can be used alongside existing HIV prevention methods such as using condoms. We also know that PrEP alone significantly reduces the possibility of becoming HIV-positive, when taken as prescribed. The strongest evidence shows taking PrEP every day works best, especially for those of us with a vagina or front hole. There is also evidence that supports taking PrEP immediately intermittently when we know we are going to be having sex. This is something we can talk about with our doctors.

PrEP does not work immediately when we start taking it: current evidence suggests it can take between 7 and 21 days for there to be enough medication in our bodies to prevent HIV, depending on our bodies and the sex we are having. For anal sex, it takes 7 days for there to be enough medication in our bodies. For vaginal sex, sharing needles, and frontal sex, it takes 21 days for there to be enough medication in our bodies.

More research is underway in Canada and globally to learn more about PrEP.  Current research is looking at the long-term impacts of using PrEP, and if PrEP still works if taken less often or in other forms, such as injections.