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expert reaction to latest ONS data on prevalence of ongoing symptoms following COVID-19 infection in the UK: 2 September 2021

The Office for National Statistics (ONS) have released the latest estimates of the prevalence people with self-reported “long COVID” using data from the UK COVID-19 Infection Survey.


Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“The latest in the monthly series of ONS bulletins on ongoing symptoms following Covid-19 infection includes estimates based on the four-week period ending on 1 August 2021. As always, the data come from ONS’s admirable Covid-19 Infection Survey (CIS). The survey collects data from a representative sample of the UK community population, so the participants are not people who have specifically put themselves forward to describe their experience. The summary section of the ONS bulletin provides a clearer description of what it’s about. It estimates the numbers of people living in private households in the UK who were experiencing self-reported long Covid symptoms during that July period. ONS define “long Covid symptoms” as “symptoms persisting for more than four weeks after the first suspected COVID-19 infection that were not explained by something else”.

“In most ways, the numbers in the latest bulletin aren’t very different from those in previous bulletins in the series – though that’s quite depressing in that there aren’t signs of things getting better. Last month I said that the numbers “continue to be alarmingly high”, and I think that’s still true. The estimated number of people in the country with symptoms lasting over four weeks, in the latest bulletin (so for four weeks to 1 August), is 970,000.  That’s comparable to the figures in the previous three bulletins (945,000 for four weeks to 4 July, 962,000 for four weeks to 6 June, 1,021,000 for four weeks to 2 May), particularly allowing for the inevitable statistical margin of error that always needs to be taken into account with survey results. This month that margin runs from 936,000 to 1,003,000. But the central estimate of 970,000 is certainly a very high number, amounting to around 1 in 65 of the whole community population. (This excludes those living in communal population such as care homes, and those aged under 2 years, who aren’t included in the ONS survey). Some of those 1 in 65 people may not have particularly severe symptoms, but two-thirds of them say that the symptoms reduce their ability to carry out day-to-day activities, and a fifth of the total say that their ability to carry out day-to-day activities is reduced a lot.  That is, about 1 in every 345 people has ongoing symptoms, that have lasted at least four weeks so far, that are restricting their day-to-day activities a lot.  In numbers, that’s 188,000 people, which is more than the entire populations of major towns such as Swindon, Swansea, Milton Keynes, Bolton or Sunderland. The total number of people affected, 970,000 is more than the population of every town and city in the UK except London and Birmingham.

“For symptoms going on at least a year, the number of people affected has been roughly stable over today’s ONS bulletin and the previous three, at 384,000 in the latest one (4 weeks to 1 August) compared to 380,000 (to 4 July), 385,000 (to 6 June) and 376,000 (to 2 May).  Again, given the inevitable statistical margin of error, really these numbers are not changing. So we’ve got 1 in every 170 people in the population who are experiencing symptoms that have gone on for at least a year. The numbers are greater than the populations of Coventry, Bradford or Cardiff. A year is a long time to be ill.  Again, about a fifth of those who have had symptoms going on for at least a year report that their symptoms reduce a lot their ability to carry their daily activities.  That’s now 83,000 people who count as disabled on the standard definition – their activities are restricted a lot by their health condition, and the condition has been going on for a long time. I suppose it’s slightly encouraging that the numbers haven’t gone up much since the previous bulletin, despite the fact that there were about 18,000 new Covid-19 confirmed cases reported between July and August last year. Some of those could now have had symptoms for more than a year, whereas they could not have been in that count in the previous bulletin because it was then less than a year since their original infection. So maybe some people who previously had the condition have recovered – but only in small numbers, and, given the statistical margin of error, actually we can’t even be absolutely sure that anyone has recovered.

“Some have previously criticised these results on the grounds that the data are self-reported – the people who report ongoing symptoms haven’t necessarily had them checked out or confirmed by health professionals. But many of the symptoms involved are inescapably subjective, and in any case there isn’t enough availability of healthcare services for people in this position for them all to be checked out by professionals anyway. So I can’t see what alternative there is to self-report, and in any case, if people are reporting on a major scale that they are suffering discomfort, illness, and in some cases disability, that’s a problem regardless of any professional involvement. Perhaps more importantly, it can’t always be clear that the continuing symptoms are caused by Covid. Most or all of the symptoms that people reported can have several different causes. In this analysis there isn’t a comparison between a group of people who are very likely to have had Covid – perhaps because they had a positive test – and a control group who are very likely not to have had Covid. There was such a comparison, for example, in the CLoCk study of long Covid in children and young people, that reported in a preprint* yesterday. There was also one in a much earlier ONS bulletin** based on data up to March this year, but as far as I know, those findings have not been updated since. In any case, the details of the questionnaires and tests used for the CIS meant that those earlier ONS results had to be based on a rather short list of possible symptoms, and a clearer comparison based on the CIS might be difficult unless the questionnaire is revised. But again, even if, for some of the people who are reporting symptoms, the cause was not a previous Covid infection, they are still symptoms that need to be taken account of and, where possible and appropriate, treated.”

* and



Dr Janet Scott, Clinical Lecturer in Infectious Diseases, MRC-University of Glasgow Center for Virus Research (CVR), said:

“This is robust data in that there is a good sample and it clearly states what it is and how it was collected.

“The weaknesses are that people have self-selected to respond which may overestimate the prevalence and also means some individuals may not have had a confirmed episode of COVID-19.

“That fatigue is the dominant symptom is in keeping with studies in which people were selected on having a positive test or attendance in hospital however.

“I note that a percentage of patients who are referred to CFS/ME clinics on investigation turn out to have another diagnosis such as sleep apnea, hypothyroidism and anaemia. There has been a lot of discussion around the similarities of CFS/ME and long lasting COVID-19 symptoms so I think it is possible that a percentage of the people in the ONS data may also have another diagnosis. It’s important for patients to receive proper investigation for symptoms and for it not to be assumes that it’s post Covid fatigue without considering other possible causes.

“More robust evidence would come from GP referrals and subsequent investigation.”



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee.  I am also a member of the Public Data Advisory Group, which provides expert advice to the Cabinet Office on aspects of public understanding of data during the pandemic.  My quote above is in my capacity as an independent professional statistician.”

None others received.

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