Scientists Finally Have A Definition For Long Covid. Here's Why It Matters

"This is a completely new disease, there are no text books, nothing that you can look up."
There are no text books when it comes to long Covid – but people are suffering.
Justin Paget via Getty Images
There are no text books when it comes to long Covid – but people are suffering.

Scientists have finally agreed on a research definition for long Covid, which will greatly help in the efforts to learn more about the condition.

The researchers, led by Professor Sir Terrance Stevenson, from University College London’s Great Ormond Street Institute of Child Health, focused their work on long Covid in children and young people. Professor Stevenson explained why a clear definition was so badly needed.

“This is a completely new disease, there are no text books, there’s nothing that you can look up,” he told BBC Radio 4′s Today programme.

“And one of the problems with new diseases is that people are all describing different things, so we wanted a research definition that could be used across the world to compare different studies.”

The agreed definition for long Covid in children and young people is as follows: “Post-Covid-19 condition occurs in young people with a history of confirmed SARS CoV-2 infection [the virus responsible for COVID-19 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.”

A consensus study on core outcomes of long Covid in adults in currently in pre-print.

The new research definition for children complements the clinical definition previously proposed by the World Health Organisation for adults. However, Professor Stevenson highlighted the difference between a clinical and research definition.

A research definition is used by scientists to help standardise research analysis, he explained. Doctors should not use research definitions to make a clinical diagnosis. For example, if a young person is presenting with possible symptoms of long Covid – but didn’t have a positive test – this may be because they were not tested at the time of their infection. The patient should still be able to access help for long Covid.

Still, the definition is a huge step forwards and adds further weight to the voices who’ve been campaigning for long Covid to be properly recognised by the medical community.

“We are certain there is something called long Covid, sometimes called post Covid-19 syndrome,” Prof. Stevenson said, when asked about naysayers. “There are definitely a group of adults and children who have persisting problems after the virus.”

It comes after researchers identified more than 200 symptoms which could be a sign of long Covid, which ranged from fatigue and brain fog to skin irritation and heart palpitations.

Image taken by Mayte Torres via Getty Images

Alongside colleagues, Professor Stevenson worked with more than 120 people – including parents, carers, young people, doctors, nurses and researchers – to come up with the definition.

Participants were asked to rate or score different symptoms and experiences, through a system called the Delphi process.

The scientists also analysed research of 6,800 teenagers. Half the teenagers had tested negative and half tested positive for Covid-19. This data was used to help whittle down which symptoms – such as persistent headaches – might be linked to long Covid, and which might be associated with the stress of lockdown, rather than past infection.

The team agreed on five statements to define long Covid in young people. These statements were agreed with a panel of 11-17 year-olds.

  • 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)

This was then summarised by the researchers into the shorter definition.

HuffPost UK previously interviewed parents of children with long Covid, many of which had struggled to access support earlier in the pandemic.

“He’s like a six-year-old in a 90-year-old’s body,” Chris Ward said of his son Thomas, who first fell ill in February 2020 with a fever, breathlessness and aches all over his body.

Layla Moran, an MP and chair of the all-party parliamentary group on Coronavirus, told HuffPost that long Covid is the “hidden health crisis” of the pandemic.

“We know long Covid affects kids too, but the way in which it affects children is even less understood than how it affects adults,” she said.

It’s why experts in the field are so relieved to have this new definition to work with.

“This work is of an extreme importance to the patients and researchers as it will undoubtably result in a substantial improvement of all future long Covid research endeavours,” said Dr Daniel Munblit, an honorary senior lecturer at Imperial College London who’s been researching the condition.

“In the absence of agreed definition of Long Covid in children researchers were applying very different definitions across the studies which did not allow for the data to be collated and properly meta-analysed. This problem, among many others, limited our understanding of Long Covid and slowed the research down.”

Dr David Strain, chair of the British Medical Association’s Board of Science, also welcomed the news, saying the definition is “vitally important in order to align the global research effort into long Covid”.

“It will allow international researchers to compare the estimates of prevalence, incidence and therapeutic benefits of different agents moving forward,” he added.

The definition for long Covid was largely patient-led, and this in itself is unusual and remarkable. It finally gives a voice to those who had their symptoms dismissed earlier in the pandemic.

“It gives ownership,” Professor Stevenson said. “It’s not somebody like me saying, ‘this is long Covid.‘’’