Thread by @apsmunro, There has never been more confusion about the role of children in [...]

There has never been more confusion about the role of children in transmission of #SARSCoV2 , and tensions are running high over implications for #schoolsreopening

Time for some clarity

@Damian_Roland and I review ALL the evidence on @DFTBubbles

https://dontforgetthebubbles.com/the-missing-link-children-and-transmission-of-sars-cov-2/

1/13

The missing link? Children and transmission of SARS-CoV-2

There is global interest in the role of children in the transmission of COVID-19. What does the evidence really say? ....

https://dontforgetthebubbles.com/the-missing-link-children-and-transmission-of-sars-cov-2/

When considering transmission risk we must consider 2 classes of factors;

Non-modifiable: The biology of the host and pathogen

Modifiable: Behavioural or environmental influence

Since we can change the latter via policy/guidance etc, we'll focus on the former

2/13

How easily to children catch the virus?

Household contact tracing studies suggest less easily than adults; by about half given the same exposure, based on 4 reviews of all the evidence (links in next tweet)

3/13

Viner et al
https://doi.org/10.1101/2020.05.20.20108126

Madewell et al
https://doi.org/10.1101/2020.07.29.20164590

Goldstein et al
https://doi.org/10.1101/2020.07.19.20157362.this

Lei et al
https://doi.org/10.1016/j.jinf.2020.08.033

4/13

Household transmission of SARS-CoV-2: a systematic review and meta-analysis of secondary attack rate

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spread by direct, indirect, or close contact with infected people via infected respiratory droplets or saliva. Crowded...

https://doi.org/10.1101/2020.05.20.20108126

There are some suggestions for biases to explain these findings why this might be the case

Some of these are not correct (e.g. "irrelevant because schools closed" or "cases missed because not symptomatic") and none explain the effect size

5/13

Whilst seroprevalence can't tell us about susceptibility (some effects will be due to exposure), most representative studies have found lower rates of seropositivity in children which would support these findings

The findings are more pronounced in young children (<10y)

6/13

Spain
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31483-5/fulltext

Switzerland
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31304-0/fulltext

Lombardy, Italy
https://doi.org/10.1101/2020.06.24.20138875

UK
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/916993/Weekly_COVID19_Surveillance_Report_week_37_FINAL.pdf

7/13

Seroprevalence of SARS-CoV-2 significantly varies with age: results from a mass population screening

Abstract Objectives Castiglione D'Adda is one of the municipalities more precociously and severely affected by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) epidemic in Lombardy....

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31483-5/fulltext

What about infectiousness once infected?

This is much harder

We have some indirect evidence from studies of viral loads, suggesting they are broadly similar in children, including those asymptomatic

But we want to know what happens in real life

8/13

2 studies on the same data from South Korea (one adjusting for shared exposure, the other not) seemed to suggest a very low attack rate from infected children, in the setting of extreme infection prevention measures

https://wwwnc.cdc.gov/eid/article/26/10/20-1315_article

https://adc.bmj.com/content/early/2020/08/06/archdischild-2020-319910

9/13

Role of children in household transmission of COVID-19

Objective Transmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19. Design and setting All paediatric COVID-19...

https://wwwnc.cdc.gov/eid/article/26/10/20-1315_article

A further study from Trento, Italy, seemed to suggest children might be more contagious than adults, but this study has some important biases (covered below)

https://www.medrxiv.org/content/10.1101/2020.07.16.20127357v1.full.pdf

https://twitter.com/apsmunro/status/1293147618307125248?s=20

10/13

What else could contribute to infectiousness?

Well there's some evidence infectiousness is correlated with symptoms, and as ~50% of children may be asymptomatic, this might reduce their contribution to transmission

https://www.medrxiv.org/content/10.1101/2020.08.31.20183095v1

https://twitter.com/apsmunro/status/1295670209479618562?s=20
11/13

What about within schools themselves?

Well, we've covered that too in detail, but see separate thread for studies on school transmission here

https://twitter.com/apsmunro/status/1298978413185703937?s=20

12/13

https://twitter.com/apsmunro/status/1298978413185703937?s=20

Conclusions
-Children about half as susceptible
-Have roughly same amount of virus
-May be less infectious, ?due to less symptoms
-Lots to learn once schools open

END

Check out the podcast too

https://open.spotify.com/show/46C01zzm2H7IvUjdqG0Ald

https://dontforgetthebubbles.com/podcast/covid-19-transmission-in-children/

https://dontforgetthebubbles.com/the-missing-link-children-and-transmission-of-sars-cov-2/

13/13

Conclusions-Children about half as susceptible-Have roughly same amount of virus-May be less infectious, ?due to less symptoms-Lots to learn once schools openENDCheck out the podcast too https://open.spotify.com/show/46C01zzm2H7IvUjdqG0Ald https://dontforgetthebubbles.com/podcast/covid-19-transmission-in-children/ https://dontforgetthebubbles.com/the-missing-link-children-and-transmission-of-sars-cov-2/13/13

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