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  • Researchers in Southern Alberta conducted a 10-year study of 2,096 people with HIV
  • 18% of participants stopped taking HIV treatment, leading to a “viral breakthrough episode”
  • Researchers identified injectable treatment, violence prevention and housing as solutions

The widespread availability of HIV treatment in Canada and other high-income countries has had a tremendous impact on the HIV pandemic. Once ART is initiated, it helps to reduce the amount of HIV in the blood. As people continue to take ART as directed, the amount of HIV eventually decreases so much that it cannot be detected with routinely used lab tests. Such a low or suppressed level of HIV is commonly called “undetectable.” Suppression of HIV allows the immune system to begin repairing itself. The power of ART is such that researchers expect that many ART users will have near-normal life expectancy.

In Southern Alberta

Despite the availability of ART and universal healthcare in Southern Alberta, some people stop taking ART. To investigate this, researchers at the Southern Alberta Clinic in Calgary analysed data collected between 2010 and 2020 from 2,096 people with HIV who had been prescribed ART. The researchers focused on participants who initially achieved a suppressed viral load (less than 40 copies/mL) and then subsequently had a viral load greater than 1,000 copies/mL. They described such a pattern as a “viral breakthrough episode” (VBE).

The researchers found that nearly 20% of the study population experienced one or more VBE. People who had VBE were more likely to be hospitalized for HIV-related complications and they had weaker immune systems (lower CD4+ cell count) and an increased risk of death.

The researchers found several factors linked to an increased risk for VBE; these are detailed later in this CATIE News bulletin. They stated that based on their findings, “novel customized care programming is required for [ART users] at greatest risk for VBE.”


When researchers analysed their data, they found that 1,710 people had achieved and maintained a suppressed viral load. However, 386 other people initially suppressed HIV and then stopped taking ART, resulting in a persistently detectable viral load (in this study that was more than 1,000 copies/mL).

Focus on VBE

Of the 386 people with VBE, 240 only had one episode.

People who had one VBE tended to be off ART for an average of 325 consecutive days. For people with multiple VBEs, such periods could last between 335 to 1,066 days.

Importantly, the researchers stated the following about all people with VBE: “On each occasion [after a VBE], the individuals managed to successfully [re-suppress their viral load], demonstrating both an interest and ability to reconnect to care and take ART successfully.”

Risk factors for VBE

The researchers found that people who were diagnosed with HIV when they were 40 years or younger were more likely to have a VBE. In general, people with the following factors were at heightened risk for VBE:

  • being heterosexual
  • injection of drugs
  • interpersonal violence
  • homelessness
  • unstable housing
  • history of incarceration
  • excess alcohol consumption

People who were Indigenous were more likely to experience a VBE than non-Indigenous people.

Risk factors for multiple VBEs

The researchers found that females were more likely to experience multiple VBEs, as were people who were homeless.

Long-term impact on health

HIV injures the immune system in at least several different ways. Therefore, it should come as no surprise that people who experienced VBE developed weaker immune systems (i.e., lower CD4+ cell counts).

The researchers found that 16% of people with VBE were hospitalized vs. 4% of people with suppressed viral loads.

During the study, 139 people (7% of the overall study population) died. Among people with VBE, 12% died and 13% of deaths were caused by HIV-related complications. Among people without VBE, 6% died and 5% of deaths were caused by HIV-related complications.

Steps needed

The research team suggested that clinics intervene “particularly after one VBE” so that the risk of further VBEs is reduced. Approaches to helping people recover from and prevent further VBEs will need to be personalized because the researchers stated that “these individuals have distinct social and emotional challenges that need to be addressed.”

For the future

The issues raised by the Southern Alberta team are likely occurring to different degrees in clinics across Canada (and other high-income countries). Possible future interventions suggested by the researchers include the following:

  • consideration of long-acting injectable ART
  • prevention of interpersonal violence
  • provision of housing

They added that the costs of such interventions “may be partially defrayed by saved costs from the ill health of VBE being avoided.”

Not mentioned but still needed

Issues not mentioned by the researchers that could also be helpful for some people include the following:

  • provision of harm reduction services
  • enhanced access to food

Indigenous people have suffered a harmful legacy from centuries of colonialism and racism. Culturally competent, trauma-informed care and implementing the calls for action raised by the Truth and Reconciliation Commission are steps that are needed.

Achieving World Health Organization goals

To help improve the health of people with HIV and eliminate AIDS, the World Health Organization (WHO) has called for 95% of people with HIV who are taking ART to be virally suppressed by the year 2025. As the study from Southern Alberta shows, a proportion of people with HIV will need help to stay virally suppressed over the long term. In order for this to happen and for WHO goals to be realized, effort needs to be made to reach and support vulnerable populations with HIV.

—Sean R. Hosein


National Centre for Truth and ReconciliationUniversity of Manitoba


2025 AIDS targetsUNAIDS


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