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COVID-19 for health professionals: Post COVID-19 condition (long COVID)

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About the condition

The World Health Organization (WHO) defines post COVID-19 condition (PCC) as occurring:

"[…] in individuals with a history of probable or confirmed SARS CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis. Common symptoms include fatigue, shortness of breath, cognitive dysfunction but also others and generally have an impact on everyday functioning. Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. Symptoms may also fluctuate or relapse over time."

The WHO published a separate clinical case definition for post COVID-19 condition in children and adolescents. It recognizes the unique health considerations of this population. Of note, the WHO indicates:

"Post COVID-19 condition in children and adolescents occurs in individuals with a history of confirmed or probable SARS-CoV-2 infection, when experiencing symptoms lasting at least 2 months which initially occurred within 3 months of acute COVID-19. Current evidence suggests that symptoms more frequently reported in children and adolescents with post-COVID-19 condition compared with controls are fatigue, altered smell/anosmia and anxiety. Other symptoms have also been reported. […] Symptoms generally have an impact on everyday functioning such as changes in eating habits, physical activity, behaviour, academic performance, social functions (interactions with friends, peers, family) and developmental milestones. Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness. They may also fluctuate or relapse over time. Workup may reveal additional diagnoses, but this does not exclude the diagnosis of post COVID-19 condition. This can be applied to children of all ages, with age-specific symptoms and impact on everyday function taken into consideration."

Several studies have reported that long-term symptoms are more common in patients who had severe COVID-19, for example, those who:

However, the condition may also occur in people who experienced only mild to moderate symptoms of COVID-19.

People experiencing symptoms of post COVID-19 condition may not have been formally tested and diagnosed with COVID-19 using:

This may be due to limited testing capacity during the pandemic and a gradual shift towards self-testing kits.

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Symptoms

Post COVID-19 condition is associated with a wide variety of symptoms across multiple organ systems. They can impact or limit everyday activities, such as school, work and caregiving. Symptoms can fluctuate in intensity, and on occasion may disappear and later reappear. Notably, some patients report that mental and physical over-exertion can exacerbate the condition.

Adults

The most commonly reported symptoms in adults include:

In October 2022, preliminary estimates from the Canadian COVID-19 Antibody Health Survey indicated that, of the adults who experienced longer-term COVID-19 symptoms:

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Children

Post COVID-19 condition typically appears in adults. However, emerging evidence shows that children may also develop chronic, persistent symptoms after COVID-19.

The most commonly reported symptoms in children include:

More research is needed on the longer-term symptoms after a SARS-CoV-2 infection in children and adolescents. In September 2022, the Public Health Agency of Canada began a 2-year collaboration with the Canadian Paediatric Society to better understand post COVID-19 condition in children.

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Mental health

Mental health symptoms, such as anxiety and depression, are commonly reported by individuals experiencing post COVID-19 condition. Encourage patients to talk to their health care provider if they think they may be experiencing symptoms of:

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Prevalence

Adults

There is still uncertainty about the prevalence of post COVID-19 condition. Several studies and systematic reviews were carried out in the initial phase of the pandemic (prior to the Omicron variant and roll out of vaccination campaigns). These found that about 30% to 40% of those not hospitalized still reported at least 1 symptom, whether it be mild or more severe, 12 or more weeks after having COVID-19.

In systematic reviews, prevalence estimates from individual studies vary widely, ranging from below 5% in some studies to around 80% in studies among those with severe initial illness. The variation in estimates is likely due to differences in:

Early evidence now suggests that infection with Omicron variants may be less likely to lead to post COVID-19 condition compared to infection with other variants. This may be partially offset by the fact that Omicron variants have been more contagious than earlier strains, resulting in higher numbers of cases of COVID-19.

In October 2022, preliminary prevalence estimates from the Canadian COVID-19 Antibody Health Survey indicated that:

These Canadian prevalence estimates are consistent with current international estimates from similar populations, such as adults:

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Children

The prevalence of post COVID-19 condition in children is not yet well established, with high variability in estimates based on a small number of studies. As more studies are conducted and new evidence emerges, these estimates will become more precise.

Risk factors

Anyone who has contracted SARS-CoV-2, the virus that causes COVID-19, can experience post COVID-19 condition, even people who had a mild SARS-CoV-2 infection.

The studies reviewed by the Public Health Agency of Canada and collaborators show that these groups appear to be disproportionally impacted by the condition:

Those with underlying chronic conditions may also be at greater risk.

Further studies are being closely watched for the potential impacts of the condition on different subpopulations, including:

  1. those who did not get 2 or more doses of COVID-19 vaccine prior to infection with SARS-CoV-2
  2. those who experience re-infections

Prevention

Currently, the best way to avoid post COVID-19 condition is to take measures to prevent SARS-CoV-2 infection. This includes measures like:

This can also protect people who are at risk of more severe disease.

Vaccination is one of the most effective ways to protect against severe COVID-19. Early evidence suggests that vaccination with 2 or more vaccine doses prior to infection with SARS-CoV-2 helps to reduce the risk of developing post COVID-19 condition.

In addition to vaccination, the Government of Canada has also taken measures to secure safe and effective COVID-19 therapies. When used properly, COVID-19 therapies can help reduce the severity of symptoms and improve outcomes for individuals who contract SARS-CoV-2.

The government has made efforts to secure a range of therapies so that people in Canada have access to the most effective treatments available. These efforts are part of a broader strategy to control the spread of COVID-19 and protect the health of people in Canada. While vaccination remains the best way to protect against severe outcomes of COVID-19, the availability of safe and effective therapies is an important tool to limit the spread of this disease.

Canada continues to monitor new developments to learn more about other preventive measures. Some international studies on post COVID-19 condition are exploring the potential use of already-approved drugs for the treatment or prevention of post COVID-19 condition. For example, nirmatrelvir combined with ritonavir will be assessed for its efficacy in treating patients with post-acute sequelae SARS-CoV-2 (PASC) or post COVID-19 condition. This is a therapy already approved for the treatment of mild to moderate COVID-19. At this time, there is insufficient rigorous evidence to guide clinical care decision making for post COVID-19 condition.

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Diagnosis and treatment

While clinical studies are underway in Canada and around the world, there are currently no regulator-level approved diagnostic tests and treatments for post COVID-19 condition. Ongoing research about what causes it, and how to diagnose and treat it, will help in the development of specific guidelines for health care professionals and patients.

The WHO, along with patients, researchers and others, developed a clinical case definition of post COVID-19 condition to assist clinicians in diagnosing the condition.

In September 2022, the WHO released living guidelines for the clinical management of COVID-19, which contain 16 new recommendations for the rehabilitation of adults with post COVID-19 condition. In the same month, the U.S. Centers for Disease Control and Prevention updated their guidance webpage for health professionals.

The provinces and territories are responsible for the management and delivery of health care services for their residents. This includes rehabilitation and treatment services for people with post COVID-19 condition. Public and private clinics that provide care to individuals with post COVID-19 condition have now opened in some provinces. These focus on interdisciplinary care, and some are connected with clinical research.

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What Canada is doing

People in Canada with post COVID-19 condition who are unable to work because of their symptoms may be eligible for financial support.

The Government of Canada continues to conduct and support scientific activities, in collaboration with other partners, to learn more about:

Budget 2022

The Government of Canada provided funding in Budget 2022 to support research and generate more evidence about the impacts of post COVID-19 condition in Canada.

The funding package includes $9 million to the Public Health Agency of Canada over 3 years to fund the development, dissemination and evaluation of evidence-based guidelines and knowledge translation tools. The guidelines and tools will cover topics related to the full cycle of the condition to support patients, health professionals and caregivers.

The budget also includes $20 million over 5 years to the new Centre for Research on Pandemic Preparedness and Health Emergencies at the Canadian Institutes of Health Research, starting in 2022 to 2023. This funding will support a dedicated Canadian post COVID-19 condition research network that will study:

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Canadian COVID-19 Antibody and Health Survey

The Public Health Agency of Canada also collaborated with Statistics Canada on the population-based Canadian COVID-19 Antibody and Health Survey. The survey was sent to 100,000 randomly selected people in Canada aged 18 years and older across the 10 provinces to:

Final results from the survey were released in the fall of 2023 and further our knowledge about longer-term COVID-19 symptoms.

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Task Force on Post COVID-19 Condition

At the request of the Minister of Health, Canada's Chief Science Advisor, Dr. Mona Nemer, convened the Task Force on Post COVID-19 Condition in August 2022 to develop a framework to manage post COVID-19 condition. The executive summary and full report are currently available. These recommendations will be critical in informing future all-inclusive action in responding to the condition, and are currently being reviewed by officials.

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Post COVID-19 Condition Secretariat

The Post COVID-19 Condition Secretariat, housed within the Public Health Agency of Canada, has been established to bring greater coordination and strategic direction to the on-going work relating to the condition. This includes coordinating a whole-of-government approach in taking action to address evidence and data gaps around the condition, along with supporting Canadians in managing and eventually recovering from it.

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