UCL News


First research definition for long Covid in children and young people

8 February 2022

The first research definition of what is meant by ‘long Covid’ in children and young people has been formally agreed in a new study led by UCL researchers.

an older woman holding hands with a sick girl lying on the sofa

The definition closely complements that proposed by the World Health Organization (WHO) for long Covid in adults. If widely adopted, it will substantially help strengthen the evidence base on this debilitating condition, say the researchers.

The slew of definitions currently used, all of which differ in number, type, and duration of symptoms, has contributed to the very wide reported variations in the estimated prevalence of long Covid in children of 1% to 51%. This has hampered research efforts to date. 

A consistently applied definition of long Covid will enable researchers to reliably compare and evaluate studies on prevalence, disease course, and outcomes, providing a more accurate picture on the true impact of the condition, explain the researchers.

In the study, led by Professor Sir Terence Stephenson (UCL Great Ormond Street Institute for Child Health), also an Honorary Paediatric Consultant at GOSH, and Professor Roz Shafran (UCL Great Ormond Street Institute for Child Health), consensus was reached among a representative panel of 120 international experts skilled in healthcare delivery (47), research (50), and lived experience (23), after careful scrutiny of 49 statements each of which was scored from 1-9, depending on their perceived importance.

These statements were sequentially whittled down in three phases (Delphi process), with the final selection of five discussed at a virtual consensus meeting. These statements were then reviewed by a panel of eight 11-17 year olds affected by long Covid to reach final agreement.

The included statements for a research definition of long Covid in children and young people were as follows: 

  • A condition in which a child or young person has symptoms (at least one of which is a physical symptom) that:
  • Have continued or developed after a diagnosis of COVID-19 (confirmed with one or more positive COVID tests)
  • Impact their physical, mental or social wellbeing
  • Are interfering with some aspect of daily living (eg, school, work, home or relationships) and
  • Persist for a minimum duration of 12 weeks after initial testing for COVID-19 (even if symptoms have waxed and waned over that period)

The researchers emphasise the need to differentiate between a clinical case definition and a research definition of long Covid. 

They said: “It is understandable that the patient groups representing people with long Covid are concerned about a definition that could restrict access to services that are needed. 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 research, which has been accepted for publication in Archives of Disease in Childhood, was supported by the NIHR GOSH Biomedical Research Centre.



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Media contact

Mark Greaves

T: +44 (0)7990 675947

E: m.greaves [at] ucl.ac.uk