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The Importance of Adherence

PrEP’s effectiveness at preventing HIV infection is directly linked to how adherent someone is. Only a handful of PrEP users demonstrated to be taking PrEP daily as prescribed have ever been infected with HIV (and most of those cases were likely due to a very rare scenario wherein the strain of HIV they were infected with was resistant to the medications present in PrEP).

However, the more doses an individual misses, the less benefit PrEP provides. For example, in the iPrEX OLE trial there was a significant decrease in HIV risk reduction amongst those who only took 2-3 pills per week when compared to those who took four or more pills per week. The effectiveness decreased even further for those who took less than 2 pills per week. 


Fortunately, demonstration projects and real-word PrEP data have demonstrated a high level of adherence by those committed to taking PrEP. Additionally, specialized health clinics with a large number of patients taking PrEP have reported no HIV infections amongst their PrEP patients despite a reasonably high rate of other STIs, reaffirming both the effectiveness of PrEP as an HIV prevention tool and the likely high rate of adherence demonstrated by those taking PrEP.

If an individual faces challenges adhering to their medication, a healthcare provider should help them identify strategies which can make adherence easier for them. Conversely, if taking a pill once a day is still a challenge for someone you might want to look at the following options:

Ongoing Monitoring & Follow-Up

While on PrEP, individuals should be engaged in ongoing discussion relating to their overall sexual health, inclusive of risk-reduction counselling, adherence support, and support or referrals related to existing psychosocial or syndemic conditions. This comprehensive, ongoing support is important for a few reasons:

  • To ensure a patient is receiving sufficient support related to any underlying issues that might affect their vulnerability to HIV and STIs (and the effective implementation of related prevention interventions)

  • To ensure they have sufficient information to prevent STI infection (as PrEP only protects against HIV)

  • To determine if they require additional support related to medication adherence

  • To determine if PrEP remains a suitable HIV prevention option for them.

In addition to this, individuals should be screened at varying points while on PrEP (30 days after they start, every three months, and yearly) to make sure they remain HIV-negative, are diagnosed and treated for STIs, and that the medication isn’t having any unintended impacts on their health. Renewal of prescription is often contingent on individuals completing required screenings.

Although some providers familiar with HIV and PrEP might choose to make some independent adjustments, the screening schedule recommended by the Albertan PrEP Guidelines is as follows:


  • *Preferred HIV test is a 4th-generation antibody/antigen combo assay. Those with signs or symptoms of acute HIV should also undergo HIV RNA testing. Healthcare providers should contact the virologist on call at ProvLab or an HIV/ID specialist to have HIV RNA testing approved.

  • †Hepatitis A and/or B vaccine should be initiated in unvaccinated individuals. Those who remain nonimmune to hepatitis B virus should be rescreened annually.

  • ‡Individuals with chronic active hepatitis B should be managed in consultation with an expert on hepatitis B virus according to Canadian guidelines.

  • §Individuals who have STIs should be offered standard therapy and follow-up as per local guidelines.


(Note: Full ongoing screening instruction and explanation found here)

Stopping PrEP

Certain situations may warrant discontinuation of PrEP. If someone receives a positive HIV test, follow-up testing should be performed and they should be referred to active HIV care. Additionally, if an individual no longer meets eligibility criteria or is having issues with proper adhering to ongoing monitoring and follow-up, then prompting a conversation about electively stopping PrEP may be necessary. Before discontinuing PrEP, it is important to consider the following points: 

  • Will the circumstances related to stopping PrEP remain static for a while or could they change in a month or two, leading the person to decide to start PrEP again? If things are prone to fast change, the person should be encouraged to wait a while before stopping PrEP.

  • The Albertan PrEP Guidelines recommend that an individual on PrEP continue to take PrEP for up to  28 days after their last potential exposure to HIV, with follow-up HIV testing performed up to 8 weeks after discontinuing their medication. 


PrEP isn’t for everybody. Some people aren’t great candidates for PrEP to begin with. Some people might only benefit from PrEP for a short period of their life, stopping when circumstances change. And others would likely benefit from PrEP for a longer period – perhaps for their entire life.


There’s nothing wrong with an individual reviewing their sexual health practices and determining that what worked for them a month or a year ago concerning HIV prevention is no longer the best option for them now. What is key is that they make this decision within the context of a comprehensive sexual health discussion with a provider they trust. And if an individual does decide to stop PrEP, they should be engaged in discussion about what other HIV prevention options they can use in PrEP’s absence. To learn more about these options, check out our full website here.