World Health Organization Sets New Long COVID-19 Definition for Children

COVID-19 Thunder Bay

The World Health Organization has released a new clinical case definition for post COVID-19 condition or ‘long COVID’ in children and adolescents.

Children and adolescents are more likely to have few or no symptoms, or develop mild illness after being infected with COVID-19. As a result, the symptoms they experience in the post-acute period and their impact may differ.

Children with post COVID-19 condition are more likely to have fatigue, altered smell and anxiety than healthy children. For both adults and children, how long the symptoms last for (at least 2 months), and how soon after the initial infection they start (within 3 months) are common in the two definitions.

The new definition is based on the latest scientific data and was developed through an expert consensus process, including the involvement of patient advocates and clinicians. WHO used a consensus-seeking approach called a Delphi exercise, for which experts and patients responded to repeated surveys. This definition applies to children of all ages, with age-specific symptoms taken into consideration.

WHO initiated the process of developing a definition specific for children and adolescents because COVID-19 affects them differently from adults.


“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.”

 About post COVID-19 condition

Anyone with COVID-19 can get post COVID-19 condition, irrespective of the severity of disease, though it is more commonly reported in those who had severe disease. The Institute for Health Metrics and Evaluation (IHME) estimated that by the end of 2021, 145 million people had developed post COVID-19 condition (3.7% of those infected with SARS-CoV-2) as defined by the WHO clinical case definition, with 15.1% of those (22 million) having persistent symptoms at 12 months after infection onset.

There remains limited information on the condition in children and adolescents, and about medium-to long-term outcomes. Using a standardized definition will contribute to a global understanding of its prevalence and allow for more comparable research studies.

WHO released the definition for post COVID-19 condition in adults in October 2021.