How should we define Long Covid?

Part of the UK COVID-19 National Core Studies
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Introduction (scroll down down to see latest posts)


The purpose of this discussion is to help develop a working definition of ‘Long COVID’ for the Convalescence Project. The aim of the CONVALESCENCE Project is to improve our understanding of Long-COVID so that we are better able to provide treatment and support.

The CONVALESCENCE team thinks that it is essential that people with experience of Long COVID are involved in developing this definition.

A key question being asked in the study is how do people experiencing Long COVID define it. People experiencing or have experienced Long COVID are essential to this work to make sure nothing significant is missed. It can also help researchers know where to look in search of answers.

This discussion will build on work done with the Project’s Patient Advisory Group.


The term ‘Long COVID’ originated with patients. It is generally used to describe a diverse set of symptoms extending beyond four weeks after symptom onset of COVID-19. Beyond this, there remains a lot of uncertainty.

The reason for this uncertainty is there remains limited understanding of what causes Long COVID, why it affects some people and not others, how if effects people differently, and why some people recover and others have progressive and/or remitting and/or ongoing symptoms. The research is still at an early stage. This uncertainty is problematic as it makes it difficult to provide appropriate advice and guidance, and develop appropriate services and support, for those living with Long COVID.

Defining Long COVID

We are using as the starting point the NICE definition of Long COVID. NICE is the UK’s National Institute for Clinical Excellence. Their aim is to improve health outcomes for people using the NHS and wider health and care services.

As per the NICE definition,

‘the term ‘long COVID’ is commonly used to describe signs and symptoms that continue or develop after acute COVID‑19. It includes both ongoing symptomatic COVID‑19 (from 4 to 12 weeks) and post‑COVID‑19 syndrome (12 weeks or more).’

You can read more about the NICE definition including the distinction between ongoing symptomatic COVID-19 and post-COVID-19 syndrome on page 5 of the COVID-19 rapid guideline: managing the long-term effects of COVID-19.

Input from the Patient Advisory Group

The project’s Patient Advisory Group met in December to have an initial discussion about a definition, or definitions, of Long COVID. Key points coming out of this discussion:

  • Questions about the timeframes used in defining Long COVID;
  • Importance of distinguishing between people who still have Long COVID with no apparent end in sight and those who have recovered;
  • Many of the definitions include reference to Long COVID as a condition that cannot be ‘explained by an alternative diagnosis’. This was considered an important part of the definition;
  • Long COVID symptoms weren’t always consistent with the initial symptoms so reference to ‘ongoing’ symptoms as part of the definition may be a problem;
  • Describing the condition as Post COVID might be useful to imply that it is something different to COVID. Long COVID may suggest that it is an extension of symptoms of the initial infection;
  • Descriptions of COVID as a respiratory condition may be unhelpful. Instead, COVID and Long COVID may sometimes be better thought of as an illness that affects whole systems of the body e.g the immune system. .

Background documents

These are google documents.

Annotated bibliography on definitions of Long COVID - for comment

Defining Long COVID - Discussion paper for Patient Advisory Group (Dec 2021) - for information

Defining Long COVID - Note of meeting of the Patient Advisory Group (Dec 13 2021) - for information

It is important that people feel comfortable and share their perspective on this topic.

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