Most of the identified published research focused on characteristics or outcomes of having post–COVID-19 condition (e.g., symptoms, quality of life) or predictors for developing post–COVID-19 condition. There were fewer studies related to preventing post–COVID-19 condition or treatments. Ongoing studies, according to published protocols, will investigate interventions to prevent or treat this condition. Notable evidence gaps included post–COVID-19 condition as it relates to people living in rural or remote areas, children and adolescents, and vaccination status. There were few economic studies, qualitative studies, and studies assessing health systems issues. Most identified guidelines regarding the diagnosis, treatment, and management of post–COVID-19 condition, including all Canadian guidelines, provided limited guidance specific to patients meeting the WHO definition. These guidelines will need continual updates as new evidence emerges.

Long-term symptoms after developing COVID-19, known as post–COVID-19 condition or colloquially as long COVID, is a new condition estimated to affect millions of people worldwide. While standard diagnostic criteria have not yet been developed, current estimates suggest that 21% to 23% of people suspected of having had COVID-19 may have symptoms 4 weeks after their COVID-19 infections and 14% may have symptoms 12 weeks post-infection. Among people with self-reported post–COVID-19, an estimated 40% may continue to experience symptoms for at least a year. To provide health care providers and people with post–COVID-19 condition advice regarding diagnosis and treatment, guidelines have been published by the National Institute for Health and Care Excellence (NICE) and by the Centers for Disease Control and Prevention (CDC). The CDC guidelines were published more recently and refer to newer data on post–COVID-19 condition. Post-COVID symptoms can affect multiple organ systems and symptoms may vary by patient characteristics such as age and sex, as well as change over time. Some people may develop more severe symptoms or have increased risk of developing other illnesses. As there are currently no known unique symptoms and no tests available to diagnose post–COVID-19 syndrome, guidelines from NICE and the CDC recommend diagnosing based on symptoms, suspected previous COVID-19 infection, and ruling out other potential causes of symptoms. Current treatment recommendations focus on multidisciplinary care and personalized treatment to address the potential range of symptoms unique to each patient. Different methods of delivering treatment have been suggested and implemented around the world, including specialized post–COVID-19 clinics and integrating treatment into primary care. Post–COVID-19 condition can result in a reduced ability to work or attend school, and reduced independence, which can impact quality of life. These effects may have a disproportionate impact on disadvantaged groups, which will have important implications for health equity. Limited evidence on the clinical effectiveness and cost-effectiveness of therapies for post–COVID-19 condition was identified. However, many trials have been registered and are in progress to address this knowledge gap.

Post–COVID-19 condition is a growing health concern and has been associated with more than 200 possible symptoms. The diverse and varied ways the condition presents clinically creates challenges for developing standard diagnostic criteria, and for health systems aiming to provide effective treatment and management supports for people. To support health care, decision-makers and clinicians understand the different clinical presentations of the condition, we scanned the evidence base to examine early approaches being used to characterize and describe subtypes of post–COVID-19 condition. Subtypes can be developed with many different disease features and patient factors, but for this report we specifically reviewed potential subtypes based on symptoms and clinical presentation. We found that some of the early approaches used to develop subtypes are based on statistical methods that group together patterns of symptoms. These studies are beginning to reveal potential subtypes based on severity of symptoms, type and co-occurrence of symptoms, and symptoms affecting different organ systems. Many reported symptoms of post–COVID-19 condition are similar to previously characterized health conditions. In some cases, subtypes of post–COVID-19 may be manifestations of those other conditions. For example, certain subtypes may present with symptoms similar to myalgic encephalomyelitis/chronic fatigue syndrome or pulmonary fibrosis. It is uncertain whether those subtypes share the same or distinct pathophysiology and whether they may benefit from similar treatments. Early evidence comparing the variant of infection and its association with potential subtypes of post–COVID-19 condition is emerging, but the findings are currently mixed. Some studies suggest that variants such as Delta and Omicron may result in different clinical presentations, while other studies have not found significant differences. Further research assessing the association between variants and subtypes is likely needed. This review provides some implications and considerations for health systems should emerging research further characterize and validate proposed subtypes. These implications may be important for improving the diagnosis, treatment, and management of post–COVID-19 condition. With estimates in Canada suggesting that more than a million people could be affected by the condition, monitoring ongoing research on subtypes may help support the development of effective and tailored treatments, and guide health systems planning across the country.

Switching to monotherapy after failure with a first antidepressant resulted in no significant difference in efficacy and tolerability among bupropion, sertraline, and venlafaxine. In treatment-resistant depression, augmentation of previous treatment with bupropion did not result in significant differences in remission compared with switching to bupropion monotherapy, augmentation with aripiprazole, or augmentation with buspirone. Switching to bupropion monotherapy or augmentation with bupropion was associated with significantly higher incidence of anxiety, decreased appetite, dry mouth, and increased blood pressure, but lower incidence of increased appetite, increased weight, somnolence, akathisia, and laboratory test abnormality compared to augmentation with aripiprazole. Augmentation therapy with bupropion or aripiprazole may be a cost-effective option relative to switching to bupropion in treatment-resistant depression. Among the monotherapies, switching to vortioxetine appeared to be the most cost-effective option relative to other medications such as agomelatine, bupropion, venlafaxine, or sertraline; bupropion, venlafaxine, and sertraline monotherapies were not significantly different from one another in terms of cost-effectiveness.

The use of electronic nicotine delivery systems and other vaping products is on the rise, and the health effects from these products remain uncertain. No evidence-based guidelines regarding the use of pharmacological vaping cessation interventions were identified. Some guidelines suggest that it may be reasonable to apply smoking cessation interventions and/or protocols for vaping cessation, but no guidance specific to the use of pharmacotherapy was identified.