Because I base my recommendation to also vaccinate children against SARS-CoV-2 primarily on the risk of long covid, I read the studies on the incidence of long covid in children with great attention. Now a long-awaited larger study on this finally came out.
Your bottom line: only about 0.8% of 6 to 17 year old children would have to deal with Long Covid after a SARS-CoV-2 infection. Moreover, the symptoms predominantly did not last longer than 4 weeks. The authors conclude:
Long COVID in children is rare and mainly of short duration.
So: Long Covid in children is rare and usually of short duration.
Trust is good, control is better
Let us therefore take a closer look at the study. I also owe important advice to Hisham Ziauddeen’s comprehensive analysis on Twitter
Now some readers, who otherwise have little to do with scientific work, may ask: Is that even necessary, this is a peer-reviewed study?. And it has appeared in a reputable scientific journal, here: the European Journal of Pediatrics.
That is true. However, it is important to note that even peer review and publication does not protect against problematic studies being published. The most recent example: a study on the effects of mask-wearing on children, which was nothing more than freely concocted nonsense. The editors only noticed after some readers (including me) wrote letters to the editors pointing out the problems. See the publisher’s website, under "comments" (top right), where you can also find my contribution at the time Similar to another study by French psychiatrists, who wanted to prove that Long Covid was actually only a matter of faith. The letters to the publisher then also made it clear here: there are not even the basics right. Today, the study is often taken as an example of what can go wrong in long covid studies.
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There is much to be said for the study
Back to the current study. First of all, it has all the arguments on its side. It is high (the authors talk about> 100.000 participants, which is a bit exaggerated, because yes, you already have 100.000 people were contacted, but only about 30 actually took part.000). And she has a control group. Reminder: many Long Covid studies are flawed by the fact that they cannot take into account the background noise of disease symptoms and thus tend to overestimate the consequences of a Covid infection.
Not only that: in this study, the comparison between those with covid and those without covid is quite reliable, because the case group (i.e. the children who were assumed to have covid) had a positive PCR test. Children who had not previously had a Covid diagnosis served as the control group. Of course, this is not perfect, because among the latter there could be children who have had an undetected covid infection. But in fact there is circumstantial evidence that this factor may not have played a major role. In fact, for the "cases", 8 – 10% indicated for the children that they had a taste or. Would have noticed loss of odor, only 0.1% in controls. Now, the parents were certainly a bit more attentive because of the Covid diagnosis, so that the difference might have been smaller in reality, but roughly one can already say: fits. In any case, the confirmation as a "case" or "non-case" by PCR is many times better than the confirmation by antibody test used in most studies so far (this method is practically worthless especially in children, that was the subject of this article).
All is well then?
Unfortunately no, and HOW problematic also this study is, becomes apparent when looking at the "supplemental material", i.e. the many lists of details that the authors could not include in the paper itself (a special thanks to Hisham Ziauddeen for your phantastic comments on twitter!)
Let’s have a look at the questions that were asked to the parents. And there we discover something remarkable: For the "cases" and for the "controls" different questionnaires with differently formulated questions were used!
The "cases" are supposed to answer how often certain symptoms persisting for more than 4 weeks "after the positive corona test" have occurred.
The control group is also asked about symptoms persisting for more than 4 weeks. However, with a different question. And they ask about symptoms that "within the last year" have occurred.
How please? Once is asked for symptoms following a SARS-CoV-2 infection asked for symptoms, another time asked for symptoms "within the last year"? These are not only completely different observation or. Reporting periods, but also different reporting occasions.
The extent to which this can have an impact can be seen, for example, in the case of chronic illnesses. As the authors show, 5% of children (in both the case group and the control group) each suffer from chronic illnesses. It is plausible that some of the children suffer from symptoms persisting for more than 4 weeks because of their underlying disease. Because of the unequal construction of the questions, these are attributed to the total burden of symptoms in the control group, but not in the case group. The same is true for other acute illnesses (from appendicitis to other infectious diseases): because of the discrepant questioning, any related symptoms only strike the control children.
These differences are serious, because: from the comparison between the frequency of the reported symptoms, the alleged "true" frequency of Long Covid is calculated afterwards.
One must be already very optimistic, if one does not want to lose faith there. In fact, the authors themselves write the following as a possible limitation of the validity of their study: "Firstly, our questionnaire was not validated in a larger pilot study."Specifically, whether the questionnaire measures what it purports to measure has never been verified. Nevertheless, I find it hard to believe that the authors did not notice the error, there is just too much evidence of it openly on the data table.
Clearly an apples to oranges comparison
And that shows in the result, which you could actually laugh about if it wasn’t so "scientifically" presented. Indeed, the authors note that when they add up the frequencies of symptoms persisting over 4 weeks in previously infected 6- to 17-year-old children, they arrive at a total (overall prevalence) of 28%.
And in the control group? There it was 27,2%
From this, the authors conclude: the incidence of Long Covid in children is – at 0.8
The authors themselves then show what nonsense they are adding up there. If they proceed in the same way with the 0 to 5 year olds, they arrive at an overall prevalence of symptoms persisting for more than 4 weeks of 14.8% in the Covid cases. In the controls it was 17.6%. The incidence of long covid in this age group is thus: MINUS 2.8%. Wonderful: a Covid infection protects against Long Covid!
At the latest here the authors should have looked again in their data collection.
However, the nonsense that results from the differently posed questions can also be seen elsewhere. For example, among the 14 symptoms, "difficulty concentrating" was also asked about. This is reported by 7.3 percent of the 5 to 17 year olds who had previously had corona. In the control group, on the other hand, twice as many complained of difficulty concentrating! Once again: At the latest here it should have dawned on the authors that they have a huge problem. In fact, this finding can only be explained if we consider that the data for the latter refer to a whole year, but for the former only to a period of time following the corona infection!
Only, what do the authors conclude instead? They note that concentration difficulties are more common in the control group than in the formerly Corona sufferers – and conclude that concentration difficulties are "not part of Long Covid". In this way, a false picture of "long covid" is created – here, concentration difficulties are clearly part of it.
Corona protects against coughing – how please?
There are quite a few covid courses with pulmonary involvement and the corresponding afterpains – i.e., such as prolonged coughing. Therefore, it would be expected that in the case group, i.e. among those previously infected with Corona, the prevalence of symptoms would be higher, more frequent Cough is reported than in the control group, or? But what do the data of this study show? Cough is reported in the Control group more frequently than in the case group, and not just a little bit, but: two and a half times more frequently. Two and a half times! In concrete terms, this means: a Corona infection protects against coughing. And quite well. Avanti dilletanti.
In reality, this study presents warning signs
Let’s try to use this study as good as possible to get some insights into Long Covid in children.
Instead of an all-clear, however, it contains clear warnings in my eyes. As the example of concentration difficulties shows, it can be assumed that the prevalence of symptoms in the control group is overestimated by at least 100% (i.e., the symptomatology attributable to Long Covid is significantly overestimated) Atis estimated). If the symptoms clearly associated with Long Covid are singled out and considered separately, there is a strong case for not taking Long Covid lightly in children either:
- Fatigue lasting more than 4 weeks was reported in 10.6% of the children affected by Covid in the study. In the control group (despite the significant overestimation due to the longer observation period) "only" 4.3% of the children were affected. So it is reasonable to assume that at least 6% of the children (but in reality probably closer to 8 to 9%) as a consequence of SARS-CoV-2 infection suffer from fatigue for a longer period of time.
- 9.4 % of the children in the case group report about three or more Symptoms lasting longer than 4 weeks. In the control group it is 4.1%. So, again, the difference is clear (and would be even clearer with clean data collection).
- About 40% of children with Long Covid continued to have Long Covid symptoms beyond 5 months after diagnosis (some for up to 13 months, which is the end of the observation period).
Of course it is to be expected that the mentioned frequencies become less in the course of time. Only: to what extent, we do not know, and this study – who is surprised – does not answer that either.
Quite sure, however, can be said that. The conclusion that the authors are spreading, and which will now of course be dragged through the press landscape, is wrong. The statement "Long COVID in children is rare and mainly of short duration" is based on a shockingly flawed study. And unfortunately, the error can only be seen if you work through the supplementary material to the study, and who does that already.
Really a pity, because how are parents supposed to get a reliable picture of the risk of corona infection for their children when scientists deliver such weak works?