Long Covid

Long Covid Is Even Less Common Than Previously Thought

In a post on long Covid back in July, I said that “estimates of the chance of reporting symptoms after 12 weeks range from less than 1% to almost 12%”. That 12% figure came from the ONS, who found that individuals who tested positive were 12 percentage points more likely than controls to report at least one symptom 12 weeks after infection.

In my post, I argued that 12% is probably an overestimate on the grounds that some people who tested positive might have been inclined to exaggerated their symptoms – to report things they normally wouldn’t have done (thanks to all the media attention on long Covid).

And I noted that a study published in Nature Medicine had observed a much smaller percentage of people still reporting symptoms 12 weeks after infection, namely 2.3%.

A new analysis by the ONS has obtained a figure almost identical to that observed in the Nature Medicine study, namely 2.5% (the difference between the blue and green lines in the chart below). This is clearly much lower than its previous estimate.

Interestingly, the reason for the discrepancy with the earlier figure isn’t the one I suggested (i.e., that some people who tested positive were inclined to exaggerate their symptoms). Rather, it’s a statistical issue.

In both their original and updated analyses, the ONS defined symptom discontinuation as two consecutive visits without reporting any symptoms. (Participants in the ONS’s survey were visited at regular intervals for the purpose of data collection.)

This means that someone would be classified as ‘having symptoms’ if they’d gone one, but not two, visits without reporting any symptoms. However, in their original analysis, participants were only followed for a median of 80 days (less than 11 weeks).

As a result, some participants who would have been classified as ‘not having symptoms’ if they’d been followed a little bit longer were still classified as ‘having symptoms’ at the end of their observation period. (In the jargon, their follow-up time was ‘right-censored’.) This is shown in the diagram below, taken from the ONS:

In the ONS’s updated analysis, which followed participants for a median of 204 days, individuals in the situation of Participant D above were correctly classified as ‘not having symptoms’ before the end of their observation period.

Using this revised method, the ONS found that less than 1% of children aged 2-11 continue to report symptoms 12 weeks after infection, with the figure rising to just 1.2% for those aged 12-16. Hence long Covid is particularly rare in children, further undermining the case for vaccinating that age-group.

While the ONS deserves credit for being completely transparent about the limitations of their original analysis, their updated analysis is still open to the criticism I mentioned above. This means that 2.5% should probably be considered an upper bound on the chances of getting long Covid, the true figure being somewhat lower.

More than Half of People ‘With’ Long Covid Might Not Have… Long Covid, According to New Research

New research by the Office for National Statistics (ONS) suggests that more than half of those who are suffering ‘from’ long Covid might not actually have it and could simply be suffering from normal bouts of ill health. The Telegraph has the story.

The ONS surveyed nearly 27,000 people, who tested positive for Covid, in the U.K. Coronavirus Infection Survey and used three different methods to estimate the prevalence of long Covid.

In one analysis, they found that 5% reported at least one symptom 12 to 16 weeks after their infection.

However, the study also found that 3.4% of people who had not been diagnosed with Covid also reported the same long Covid symptoms.

Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, said: “That’s not all that much less than the 5.0% for the infected people, which does show that having one or more of these symptoms isn’t uncommon regardless of Covid.”

Long Covid symptoms are fever, headache, muscle ache, weakness/tiredness, nausea/vomiting, abdominal pain, diarrhoea, sore throat, cough, shortness of breath, loss of taste and loss of smell.

However, the ONS said that such conditions were experienced regularly within the general population.

A second analysis found that just 3% of people reported continuous symptoms for at least 12 weeks after an infection, compared to 0.5% of the control population.

However, in a third analysis, when the group was asked to self-identify as suffering from long Covid, 11.7% said that they believed they had the condition, with 7.5% saying the condition limited their day-to-day activities.

When confined to only people who had suffered symptomatic Covid, the number saying they suffered from the condition rose to 17.7%.

Previous studies have suggested up to a fifth of people catching Covid will suffer from long-term after-effects.

The ONS said that depending on which measure was used, the data showed between three and 11.7% of Covid cases still had symptoms 12 weeks after an infection.

Worth reading in full.

Professor Sir Terence Stephenson Spins His New Study to Exaggerate Long Covid and Trivialise the Impact of Lockdowns in Children

The latest findings of the world’s biggest study into ‘Long Covid’ in children and young people (CYP) – the CLoCk study from University College London – have been published as a pre-print.

Surveying 11 to 17 year-olds who tested positive for COVID-19 in England between September and March, the researchers found that the condition is not common in children and young people. This is in line with other studies into Long Covid.

As with earlier studies, symptoms were prevalent in those who tested negative as well as those who tested positive, complicating the picture of the condition which the authors acknowledge lacks clear definition.

Further confusion was sown by the fact that reported symptoms increased rather than decreased after three months, leaving the authors puzzling over the explanation.

Three months after the SARS-CoV-2 test, the presence of physical symptoms was higher than at the time of testing. This finding emphasises the importance of having a comparison group to objectively interpret the findings and derive prevalence estimates. Although 64.6% of test-positives reported no symptoms at time of testing (compared to 91.7% of test-negatives), they did not continue to remain asymptomatic, with only 33.5% of test-positives (and 46.7% of test-negatives) reporting no symptoms at three months. This finding warrants further exploration and could be due to self-selection into the study because they were experiencing on-going symptoms, recall bias, external factors relating to the pandemic such as returning to school and exposure to other sources of infection, and the actual trajectory of the illness, although this wouldn’t explain the high prevalence among test-negative CYP.

In terms of physical symptoms – tiredness, headaches, shortness of breath, loss of smell, and so on – the researchers found there was a somewhat elevated prevalence of these among the test-positive compared to the test-negative, though both had increased over the three month period.

Three months after the SARS-CoV-2 test, the presence of physical symptoms was higher than at baseline in both groups; 66.5% of test-positives and 53.4% of test-negatives had any symptoms whilst 30.3% of test-positives and 16.2% of test-negatives had 3+ symptoms. The symptom profile did not vary by age: for both 11-15 year-olds and 16-17 year-olds the most common symptoms among test-positives were tiredness, headache and shortness of breath and, among test-negatives, tiredness, headache and the unspecified category of “other”. Again, the prevalence of tiredness and headache was consistently higher in the test positives, 39.0% and 23.2% versus 24.4% and 14.2% in negatives, respectively. Prevalence was higher for 16-17 year-olds; for example, 46.4% of test-positives reported being tired compared to 29.6% of test-negatives.

The 14% difference reported here between the 30% of test-positives and the 16% of test-negatives who had three or more symptoms at three months is likely to be the study’s most accurate estimate of the prevalence of Long Covid in the sample population.

However, as the BBC’s Nick Triggle notes, the low response rate and selection bias towards the unwell in the survey may mean the true prevalence of Long Covid is more like 2%.

A Doctor Asks: The Data Is Looking Good, So Why the Doom-Mongering?

There follows a guest post from our in-house doctor, formally a senior medic in the NHS, analysing the latest NHS England data packet.

Once a month, the NHS releases a more detailed summary of COVID-19 related data than provided in the regular daily updates. Although the data set is far from complete, the monthly packets provide a better impression of what is really happening in hospitals than the daily snapshot. I find this month’s information particularly interesting. Apologies in advance to readers for reverting to a more data-driven ‘chart fest’ format for my latest contribution – but stick with it, because there are some important messages here which have not been widely reported so far.

Take a look at Graph One. This rather complicated graphic shows daily admissions in the vertical orange bars and paired daily discharges in the vertical blue bars. Readers will notice that on every day between April 7th and June 30th, there were more discharges than admissions.

The grey line with the secondary y-axis to the right of the chart shows the total number of ‘COVID-19’ patients in hospital on each given day. For the first period from April 7th to May 25th, this was on a falling trend – that’s what one would expect if there were more discharges than admissions each day.

From May 26th to the end of June, however, the total number of patients in hospital ‘with COVID-19’ was on an upward trend – but on each day of the series, there were still more discharges than admissions. How can that be?

I’ve discussed this issue with colleagues and there are only three interpretations we can think of. One is that there are a very large number of patients contracting COVID-19 in hospital who came into hospital without the virus. The second is that some of the ‘discharges’ are in fact patients who were never admitted to hospital at all, but seen in A&E and then sent home. The other is that the data quality is very poor and gives a misleading impression of the true picture.

How Common Is Long Covid?

Estimates of the prevalence of long Covid – where symptoms persist for more than four or more than 12 weeks after infection, depending on the exact definition – vary dramatically.

Before getting to the estimates, what kind of symptoms are we talking about? All of the following have been reported: abdominal pain; cough; diarrhoea; fatigue; fever; headache; loss of taste; loss of smell; myalgia; nausea or vomiting; shortness of breath; and sore throat.

The ONS has documented that almost 14% of people who test positive for COVID-19 continue to report at least one symptom 12 weeks later. This estimate is based on data from the Coronavirus Infection Survey (CIS) – a large, random sample of UK residents living in private households. Here’s the ONS’s chart:

The control participants comprise individuals who took part in the CIS but were unlikely to have been infected. Note that only 2% reported at least one symptom on the relevant date. This seems to suggest that fully 12% of people who test positive for COVID-19 go on to experience long Covid (over and above the background rate).

However, while the CIS is a high-quality sample, the 12% figure isn’t necessarily correct. That’s because the symptoms are self-reported, and we don’t have any information on severity.

Due to the amount of media attention long Covid has received, CIS participants who tested positive might have been inclined to exaggerate their symptoms – to report things they normally wouldn’t have done. In other words, some of their symptoms might be more psychosomatic than physical.

Long Covid ‘Symptoms’ in Teens are No Less Common in Those Who Haven’t Had the Virus – Study

The risk of long Covid – the persistence of Covid symptoms like fatigue and headaches for three months or more – has been used to justify health interventions including with younger people who are not at elevated risk from acute infection. For instance, Health Secretary Matt Hancock suggested in April that young people should get vaccinated to avoid long Covid, saying Covid was a “horrible disease” and long Covid affected people in their 20s “just as much” as any other age group, sometimes with “debilitating side effects that essentially ruin your life”.

New research, however, casts doubt on whether symptoms attributed to long Covid are really associated with COVID-19 at all, at least in adolescents.

The study, which has yet to be peer-reviewed, is the first (as far as the authors are aware) to compare the incidence of long Covid symptoms in those who have and have not had the virus, defined in terms of having detectable antibodies. It involved 1,560 secondary school pupils aged 13 to 18 in Eastern Saxony (median age 15) enrolled in the SchoolCovid19 study since May 2020. All have been tested for antibodies throughout the study and in March and April 2021 completed a 12 question long-Covid survey regarding “the occurrence and frequency of difficulties concentrating, memory loss, listlessness, headache, abdominal pain, myalgia/arthralgia, fatigue, insomnia and mood (sadness, anger, happiness and tenseness)”.

The findings are remarkable. Of 1,560 pupils, 1,365 (88%) were seronegative (no IgG antibodies detected) and 188 (12%) were seropositive. Each of the long Covid symptoms was present in at least 35% of the pupils within the seven days before the survey. Crucially, however, there was no statistically significant difference in reported symptoms between seropositive and seronegative pupils (see chart above).

These findings suggest that, in adolescents at least, the prevalence of long Covid is considerably exaggerated, and that the presumed symptoms of long Covid are common to those who have and have not had the virus. One possibility is that this is a background rate for teenagers. However, the authors are struck by the high incidence of the symptoms and suggest they may be linked to the lockdown conditions, saying they confirm “the negative effects of lockdown measures on mental health and well-being of children and adolescents”.

Because the study was only among adolescents it did not include any who had suffered severe illness or been hospitalised, which is where some earlier research on long Covid has focused.

For adolescents it suggests that the threat from long Covid has been greatly overdone, and that the apparent symptoms of the condition are much more likely to be caused by lockdowns than by a viral infection.