1. Updated thread on children & #COVID19, summarising recent research.

Summary: further evidence children and adults are equally susceptible, and similarly likely to transmit. Schools have been a driver of the second wave in Europe, Canada, and elsewhere.
#edutwitter #auspol
2. First, a recap. Given similar exposure, children and adults appear equally susceptible to infection, and also appear to transmit at a similar rate. School transmission has been increasing in many countries. https://twitter.com/DrZoeHyde/status/1312392762445066243
3. Because children are more likely to be asymptomatic than adults, infections in this age group can be difficult to detect.

I wrote an article about how this has affected some of the research to date, and why we mustn’t overlook schools. https://twitter.com/DrZoeHyde/status/1321377321480196097
4. Children are often tested less than adults, which has created a perception they are less likely to be infected.

But when antibody tests are used to look for evidence of a past infection, children, teenagers, and adults appear similarly susceptible. https://twitter.com/DrZoeHyde/status/1330845806706847744
5. In Germany, PCR testing had initially suggested young children were less likely to be infected than teenagers.

But recent antibody testing has showed no difference. It seems young children just weren’t getting tested. https://twitter.com/DrZoeHyde/status/1322198476923416576
6. But even antibody testing can have problems, because it often looks for a marker of viral replication.

Because children often fight the virus off quickly (which means less viral replication), false negatives may be more likely in children than adults. https://twitter.com/DrZoeHyde/status/1324386054443429888
7. In this study of a Melbourne family, the children didn’t test positive with either a PCR test or a standard blood antibody test, despite being infected.

But a saliva antibody test was positive, and there was also evidence of a cellular response. https://twitter.com/DrZoeHyde/status/1328731664239841280
8. It’s unclear whether the children of the Melbourne family were infectious. Such mild cases (where repeated PCR tests are negative) might not be, which is good news.

But in general, children, teenagers, and adults appear to pose a similar transmission risk.
9. The largest contact tracing study published to date suggests even young children transmit at meaningful rates.

Attack rates by age of index case:

0-4: 6.3%
5-17: 7.3%
18-29: 6.5%
30-39: 7.3%
40-49: 8.0%
50-64: 8.2%
65-74: 7.2%
75-84: 8.5%
>=85: 8.1% https://twitter.com/DrZoeHyde/status/1311687988032667649
10. A prospective study conducted by the CDC also showed children, adolescents, and adults were similarly likely to infect other household members. https://twitter.com/DrZoeHyde/status/1322429296577634304
11. Most of the children in those studies were probably symptomatic, and it’s not clear if these results apply to asymptomatic children, who might be less likely to transmit.
12. However, at least some asymptomatic children can transmit the virus, as shown in this study.

This outbreak would not have been detected if a symptomatic adult had not been tested. https://twitter.com/DrZoeHyde/status/1315960704726298626
13. We would therefore expect to see transmission occurring in schools, at least when community transmission is high.

When good records are kept, we see this is clearly occurring. https://twitter.com/DrZoeHyde/status/1331506436132667392
14. As community transmission has increased, school outbreaks have become common.

Since writing the tweet below (on 4 December), the number of school clusters reported in the media in Germany has now increased to at least 509. https://twitter.com/DrZoeHyde/status/1334536401338044417
15. Outbreaks in primary schools have been less commonly reported to date (possibly because they have been less likely to occur, or possibly because they are harder to detect).

However, outbreaks do occur in these settings. https://twitter.com/DrZoeHyde/status/1330840722430328832
16. The differences we have seen for younger children and teenagers may simply reflect the level of community transmission.

Primary and high school students were similarly affected in a region with high levels of community transmission in Belgium. https://twitter.com/DrZoeHyde/status/1327959154066001921
17. In Austria, a surveillance study of approximately 14,800 students and 1,200 teachers found that a similar proportion of primary and high school students (up to age 15) were infected. https://twitter.com/DrZoeHyde/status/1327272945513762816
18. Transmission in schools can therefore be expected to contribute to community transmission to some extent.

In Montreal, this may have been significant. https://twitter.com/DrZoeHyde/status/1324606718580420608
19. Similarly, in Israel, school reopening appeared to play at least some role in accelerating the epidemic there. https://twitter.com/DrZoeHyde/status/1321078130400870404
20. A role for schools in driving the epidemic is also suggested by data from England.

Infections fell when schools closed for the half-term holidays, and then increased again when schools reopened.
https://www.imperial.ac.uk/news/208413/coronavirus-prevalence-remains-high-some-evidence/
21. Following this, a short lockdown (excluding schools) was introduced in England. Case numbers started to fall, except in children and teenagers, where they continued to increase.

The UK Government continues to maintain masks are unnecessary in schools. https://twitter.com/DrZoeHyde/status/1333338399508361217
22. Teenagers are now the most frequently infected age group in England. https://twitter.com/DrZoeHyde/status/1332575662863904768
23. None of this is particularly surprising. This pattern has been observed across many countries. https://twitter.com/DrZoeHyde/status/1320755362685808641
24. Here, the president of the Robert Koch Institute (the German equivalent of the CDC) explains children can bring the virus to school and infect their peers, who then take the virus back out into the community.
25. The policies in place in many countries are clearly not working. But the solutions are not complex, and have already been identified. https://twitter.com/DrZoeHyde/status/1327584385822912513
26. Much more detail can be found in these comprehensive guidelines developed by the Harvard T. H. Chan School of Public Health.

➡️ https://schools.forhealth.org/wp-content/uploads/sites/19/2020/06/Harvard-Healthy-Buildings-Program-Schools-For-Health-Reopening-Covid19-June2020.pdf
27. Interventions to protect schools don’t have to be expensive.

The Max Planck Institute for Chemistry has developed a simple aerosol removal system that costs about 200 Euros to make. https://twitter.com/DrZoeHyde/status/1331499374795321344
28. I’ve summarised a lot of this information in a (hopefully) easy to read article here: https://twitter.com/DrZoeHyde/status/1331164177843384320
Here's the unroll.

Summary: further evidence children and adults are equally susceptible to #SARSCoV2, and similarly likely to transmit. Schools have been a driver of the second wave in Europe, Canada, and elsewhere.
https://threadreaderapp.com/thread/1336612124835995648.html
#edutwitter #COVID19 #Schools
Thread by @DrZoeHyde on Thread Reader App

Thread by @DrZoeHyde: 1. Updated thread on children & #COVID19, summarising recent research. Summary: further evidence children and adults are equally susceptible, and similarly likely to transmit....

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