Thread by @NahasNewman, 1/ The most important evidence regarding pediatric transmission comes from Iceland, and [...]

1/ The most important evidence regarding pediatric transmission comes from Iceland, and their study published in NEJM.

Be suspicious of any expert ignoring this paper and discussing anecdotes instead.

https://www.nejm.org/doi/pdf/10.1056/NEJMoa2006100?articleTools=true

2/ The data for the study come from Iceland’s systematic screening of its population.

Was based on a population-representative sample (identified without respect to symptomatic status), and a sample based on presence of symptoms.

3/ The study isolated SARS-CoV-2 samples from every positive case, sequenced genome of virus, and tracked the mutation patterns.

This analysis, along with contact tracing, allowed the authors to identify definitively who passed the virus to whom.

This is unique.

4/ Based on this, the senior author concluded that

“[E]ven if children do get infected, they are less likely to transmit the disease to others than adults. We have not found a single instance of a child infecting parents.“ https://www.sciencemuseumgroup.org.uk/blog/hunting-down-covid-19

Coronavirus: Hunting down COVID-19

Roger Highfield, Science Director, talks to Kari Stefansson, whose genetic sequencing project has revealed how the UK infected Iceland, that children don’t seem to infect parents, and how to control...

https://www.sciencemuseumgroup.org.uk/blog/hunting-down-covid-19

5/ This is huge.

The genetic analysis in this study is the most direct evidence of the direction of transmission. And this evidence shows that children must be less likely to transmit than adults.

No other way to view this. These data are basically irrefragable.

7/ Note: your cousin’s friend who heard about some stuff . . . almost certainly didn’t sequence any genomes.

8/ The same is true of the news reports of isolated instances of school outbreaks.

Though these accounts usually proclaim hysterically that children are super-spreaders, their conclusions seem never to be based on actual tracing (much less deeper genetic analyses). Never.

9/ Yet these stories are getting more press than Iceland.

This is especially weird here, as Iceland is not an outlier. It’s results are also corroborated all over the world.

In fact, at this point so many datasets on point, it’s overwhelming.

Here are two examples.

9/ Ireland. Researchers compared infected children with infected adults.

Despite identifying a total of 722 contacts for the infected children, the study found not a single instance of an infected child passing on the virus.

10/ In contrast, the adults who were infected, had many fewer contacts – 102 – and yet did pass on the infection. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7268273/

No evidence of secondary transmission of COVID-19 from children attending school in Ireland, 2020

As many countries begin to lift some of the restrictions to contain COVID-19 spread, lack of evidence of transmission in the school setting remains. We examined Irish notifications of SARS-CoV2 in...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7268273/

10/ Netherlands. A report by the ministry of health in the Netherlands, based on extensive contact tracing data, also found almost no disease spread by infected patients 20 and under at all.

The authors of the study concluded:

11/ “Data from the Netherlands confirms . . . children play a minor role in the spread of the novel coronavirus. The virus is mainly spread between adults and from adult family members to children. The spread of COVID-19 among children or from children to adults is less common.”

12/ Here is the paper from the Netherlands and a helpful chart.

https://www.rivm.nl/en/novel-coronavirus-covid-19/children-and-covid-19

13/ Thus, we are faced with two hypotheses:

(1) children play an equal role in transmission

(2) children play a meaningfully reduced role in transmission.

14/ Hypothesis (1) explains the stories out Israel and other isolated cases of seeming pediatric spread.

But it can NOT explain the data out of Iceland, Ireland, France, Netherlands, Australia, Denmark, and numerous other datasets.

Thus, it explains only a subset of the data.

15/ Hypothesis (2) however can explain ALL the data.

It can explain Ireland, etc. AND the stories of pediatric transmission (bc it doesn’t deny possibility of pediatric spread, just suggests its lower prob).

16/ In fact, looking at the set of evidence taken as a whole, the obvious hypothesis that jumps out is NOT that children must play an equal role in transmission.

But rather, that children must play a reduced role.

17/ Thus, the alarmist claiming kids are super-spreaders are trying to base policy on a hypothesis that looks only at a sliver of the data.

That would be bad enough.

But what they are doing is worse.

18/ They are not just ignoring tons of data. But ignoring the most systematic and in favor of the most anecdotal.

Ignoring the genetic analysis out of Iceland bc of an impressionistic news report is not science. It’s sleight of hand. And a poor one at that.

19/ PS I don’t discuss risk *to* children here (but rather risk *from*). That is because at this point the first issue is settled. The risk to children is staggeringly low, as @d_spiegel has put it.

https://twitter.com/apsmunro/status/1278714292343365632?s=21 https://twitter.com/apsmunro/status/1278714292343365632