In recent decades, education and medical advancements have drastically reduced the number of new HIV infections in Canada and the U.S. While there’s still no cure for the virus, it’s very treatable. With adequate care, an HIV-positive person can live a full and healthy life—and effective first-line treatments can suppress a person’s viral load to the point that it’s undetectable and untransmittable . 
 

Treatment for HIV also includes measures that prevent infection before and after exposure. These are pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP). PrEP can be used by people who are at a risk of contracting HIV to protect against new infections. PEP is used immediately after suspected exposure to HIV and can prevent an infection even if the virus has entered the body. 
 

PrEP has grown in popularity, but public health messaging is still largely targeted at queer men. Many women don’t even realize they’re eligible for the drug: a survey of cis and trans women in Ontario, for example, found that only 51 percent of respondents were aware of PrEP, despite the fact that half the group surveyed was at high risk for HIV. More than 90 percent of respondents had never been offered PrEP by their doctors. 
 

To help demystify the topic, Script spoke to Dr. Anastacia Tomson about PrEP and what women should know about the drug.
 

What is PrEP and how does it work?

“PrEP is—as the name suggests—a preventative intervention,” Dr. Tomson says. If a person taking PrEP is exposed to HIV, the drug will begin attacking the virus immediately and can destroy it before it reproduces enough to become a permanent infection.

Health Canada has approved four PrEP formulations: two oral tablets and two long-acting injections. Oral PrEP pills are taken once per day. They can be taken “as-needed” ahead of expected exposure, which is known as on-demand or event-based dosing. This type of PrEP involves a dose of two pills two to 24 hours before a sexual encounter. This is followed by one pill 24 hours after your first dose, and another 24 hours after that. This is also known as 2-1-1 dosing.
 

Long-lasting, injectable PrEP is a recent development. One version approved in 2024 contains cabotegravir and lasts for two months. The latest version, approved this year, contains lenacapavir and lasts for six months. The injections are delivered by a medical professional.

There are ongoing trials for long-term oral PrEP. These include a once-a-month oral pill—but they haven’t been approved for wider use. 
 

Do women need PrEP? 

Despite advances, new HIV infections have been rising in Canada. In 2024, new infections rose by a worrisome 23 percent, prompting advocates to fear that progress is at risk.
 

Women accounted for almost one third of new Canadian HIV infections in 2020. Indigenous women, trans women and women who use drugs face a particularly high risk. Discrimination, lack of healthcare access and unemployment all contribute to this higher risk.  

So, broadly speaking, women do need PrEP—especially those who are at a heightened risk of HIV. And they can use it: PrEP is effective for people of all genders, whether they are cis or trans. Despite this, data from nine Canadian provinces shows that only two percent of people using PrEP are women.
 

So how safe and effective is PrEP, exactly?

The short answer is very effective.

When used correctly, PrEP reduces a person’s chance of contracting HIV by up to 99 percent. But, Dr. Tomson notes, transmission risk “depends on the kind of sexual encounter a person is having.” Receptive anal sex, for example, carries a higher risk than receptive vaginal sex. 
 

She also adds that while PrEP’s efficacy in women is less well-studied than its efficacy in men, “the mechanism is the same, so it works.” 

Notably for trans women, PrEP is not known to negatively interact with hormone replacement therapy. And there is no evidence that the drug is less effective in trans people than it is in cis people. Studies have also shown that injectable PrEP is effective in trans women and in cis women, but research is ongoing. 

PrEP is not known to pose risks to pregnancy or breastfeeding. Oral and injectable PrEP formulations reduce HIV transmission between pregnant people and fetuses, as well as parent-child transmission during breastfeeding. 
 

Is PrEP right for me?

Before starting PrEP, it’s important to balance out the benefits against the potential drawbacks. 

PrEP can benefit many people. People who have unprotected sex without knowing their partner’s status gain a lot of protection from PrEP because the majority of new HIV infections in Canada occur through sexual contact. This includes people who have casual sex with multiple partners and full-service sex workers who do not (or cannot) use condoms.
 

People who have HIV-positive sexual partners can take PrEP as an extra layer of protection. An HIV-positive person with an undetectable viral load won’t transmit the virus via sexual contact, but PrEP protects against unseen changes to viral load, or failures in barrier methods like condoms.
 

However, starting a new medication comes with considerations. Cost, access and convenience are all important factors. PrEP is only available with a prescription, for example, and injectable PrEP must be administered by a medical professional. 
 

Some people find that taking a pill every day is inconvenient, for example. On-demand PrEP also requires a prescription and doesn’t provide sustained protection. Access barriers and adherence to medical schedules all affect the long-term effectiveness of PrEP—if a person doesn’t take their medication as prescribed, the drug will be less effective. 

Lastly, PrEP is generally well-tolerated, but it can cause side effects such as diarrhea, headaches, dizziness, nausea and indigestion. That said, most common side effects occur in less than 10 percent of people, are mild and resolve on their own. 

A very small number of people who start PrEP may experience bone or kidney problems. Anyone who suffers serious side effects from PrEP should consult their doctor.
 

Why do so few women take PrEP?

Dr. Tomson says that women’s low access to PrEP is due to social barriers. Because the most prominent public health messaging targets cis men who have sex with men, other populations—especially trans people and cis women—can be left out of the research and intervention picture.

The fact that many clinicians don’t talk to patients who are women about PrEP also poses a problem, she says. “Providers who aren’t adequately educated and informed about PrEP and its applications are another significant barrier. [Patients] can’t ask for PrEP if [they] don’t know what PrEP is.” 
 

Then, women must deal with the barriers that anyone looking to access PrEP faces, regardless of their gender. “Where are these services being rolled out?” Tomson asks. “Do people have to travel for them? Do they have to take off work for them? Are they going to a facility where just being there makes them a target because it’s very visible and impacts their confidentiality?"

How can I start PrEP?

If you’ve decided that PrEP is for you, there are several ways to start. Where and how often you can access it matters because PrEP is usually taken continuously. Doctors and nurse practitioners in Canada can prescribe PrEP directly. Hospitals, clinics and specialist HIV clinics can also provide PrEP or direct clients to providers who can assist them. Individual provinces may have their own systems to make PrEP access easier. Ontario and Alberta have PrEP information websites with guidelines and lists of local PrEP prescribers, for example.
 

Before prescribing PrEP, clinicians may require tests for HIV and hepatitis, as PrEP can cause hepatitis flare-ups if managed incorrectly. You should be able to work with your clinician to find a PrEP regimen that fits your needs and to get started. 
 

When it comes time to talk to your healthcare providers, Tomson says that a good provider has the responsibility to make patients feel comfortable speaking up. As a patient, though, you shouldn’t be afraid to advocate for yourself. “The best way to do it is to ask very directly and very plainly. Tell your clinician ‘I heard about PrEP’ or ‘I’m interested in PrEP,’” Tomson says. “Ask them ‘Is this something that you can help me with and, if you can’t, would you be able to point me in the direction of someone who can?’”