Researchers agree on first formal definition of long COVID in children

An international group of experts has endorsed a formal research definition of long COVID in children and young people for the first time.

The condition, also known as post-acute COVID-19 or post-COVID-19 condition, occurs when long-term symptoms persist following a COVID-19 infection.

In a paper accepted for publication in Archives of Disease in Childhood, a team of 120 experts worked together with a panel of 11-17-year-olds affected by long COVID to agree on the new definition.

The proposed definition reads:

“Post-COVID-19 condition occurs in young people with a history of confirmed SARS CoV-2 infection, with at least one persisting physical symptom for a minimum duration of 12 weeks after initial testing that cannot be explained by an alternative diagnosis. The symptoms have an impact on everyday functioning, may continue or develop after COVID-19 infection, and may fluctuate or relapse over time.”

Long COVID is a poorly understood condition, especially in children and young people.

Without a clear and accepted definition, it is difficult to reliably compare research and evidence about long COVID.

This lack of consensus has led to large variations in the reported or estimated prevalence of long COVID in children and young people, the authors of the new paper say.

They hope that the new definition will make it easier to conduct reliable research to understand the prevalence, severity and outcomes of long COVID.  

The World Health Organization (WHO) released a clinical case definition of post-COVID-19 condition in adults using a similar process back in October 2021.

“Post COVID-19 condition occurs in individuals with a history of probable or confirmed SARS CoV-2 infection, usually three months from the onset of COVID-19 with symptoms and that last for at least two 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 two definitions are very similar, with minor differences including the duration of symptoms – at least two months in the WHO adult definition versus at least 12 weeks in the new children’s definition – and the inclusion of “probable” as well as “confirmed” SARS-CoV-2 infection in the adult definition.

A research definition does differ from a clinical case definition – as the name implies, research definitions are used to guide research but not clinical diagnosis.

In other words, the new paper is not necessarily calling for the new definition to be relied on when diagnosing young patients with long COVID or determining access to services for long COVID patients.

“In our view, the decision whether a child or young person can see a healthcare professional, access any support needed, or be referred, investigated or treated for long COVID should be a shared decision involving the young person, their carers and clinicians,” the paper states.

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