As many as one in seven children who get coronavirus could have symptoms almost four months later, according to the world’s largest study on long Covid in children.
People who tested positive were twice as likely to report three or more symptoms 15 weeks later than those who tested negative, research led by University College London and Public Health England found.
Lead author Professor Sir Terence Stephenson said he feels “reassured” by the data, which he said shows it is “nowhere near what people thought in the worst-case scenario”.
The researchers said their findings will be presented to the Joint Committee on Vaccination and Immunisation (JCVI) – which has yet to give a decision on extending the Covid jabs rollout to all 12 to 15-year-olds.
While a researcher involved in the study said it is “unlikely” their work would form the basis of a decision to widen the vaccine programme because it looked at symptoms rather than severe disease, some experts have called for the findings to be considered as part of the debate on offering jabs to younger people.
The research looked at almost 7,000 children aged 11 to 17, made up of those who had a positive PCR test result between January and March and a group who tested negative in the same period.
When surveyed around 15 weeks after their test, 14% more young people in the positive group had three or more symptoms, including unusual tiredness and headaches, than those who tested negative.
One in 14, or 7%, more in the positive group had five or more symptoms, the study showed.
Researchers said their data suggests that between September and March at least 4,000 – and possibly as many as 32,000 – teenagers of the total population of this age group who tested positive in England might have had three or more symptoms linked to the infection some 15 weeks later.
While there was little difference in the mental health and wellbeing scores between children who tested positive compared to those who tested negative, researchers said a high proportion in both groups reported being a bit or very worried, sad or unhappy.
This accounted for 41% of those who tested positive and 39% of those who tested negative.
Sir Terence, Nuffield Professor of Child Health at the UCL Great Ormond Street Institute of Child Health, said: “There is consistent evidence that some teenagers will have persisting symptoms after testing positive for SARS-CoV-2.
“Our study supports this evidence, with headaches and unusual tiredness the most common complaints.
“The difference between the positive and negative groups is greater if we look at multiple symptoms, with those who had a positive test twice as likely to report three or more symptoms 15 weeks later.”
The Children and young people with Long Covid (CLoCk) research will carry on, with analysis of results at six months, a year and two years from the time of the person’s PCR test.
Sir Terence said while he is reassured by these early findings, he remains “very concerned” that there could be young people who are “severely affected”.
He added: “That’s something that we’ll return to when we study young people at six months.
“But there will be some young people who are completely bedridden or remain very short of breath or have daily headaches, and I wouldn’t want to diminish that, but we’re reporting kind of aggregate numbers.
“I think overall it’s better than people would have guessed back in December.”
The study also involves researchers at the universities of Edinburgh, Bristol, Oxford, Cambridge, Liverpool, Leicester, Manchester as well as King’s College London, Imperial College London, Public Health England, Great Ormond Street Hospital and University College London Hospitals (UCLH).
Dr Liz Whittaker, senior clinical lecturer in paediatric infectious diseases and immunology at Imperial College London, said the JCVI’s decision on extending the vaccine rollout is likely to be based on the risk of severe disease from the virus compared with risks of the vaccine, rather than the data in this study which relates to long Covid.
Dr Nathalie MacDermott, clinical lecturer in paediatrics at King’s College London, said the study “clearly demonstrates that children and young people are susceptible to persistent symptoms” from the virus.
She added: “It is important that long Covid be considered amongst the other negative outcomes of Covid-19 infection (death and hospitalisation) when decisions are made in regard to protecting the population from Covid-19, particularly in relation to extending Covid vaccination to our younger population.”
Danny Altmann, professor of immunology at Imperial College London, said the study showed the “risk of long-term debilitating illness appears real and significant” in children.
He added: “The data offers significant new input to global debates about how extensively we need to control infections in children, given that lethal disease is so rare relative to older groups.
“The answer seems to be that large numbers of children are paying a very high price for Covid-19 infections. Studies such as this need to inform our policy discussions of risk-benefit in schools as we consider masks, ventilation and vaccine rollout.”
Health minister Lord Bethell said: “Most people who catch Covid-19 make a full and quick recovery but we know some continue to suffer from symptoms for months after being infected.
“That’s why we are backing vital research like this to help build our understanding of long Covid so we can protect adults and children from its effects.”