Thread by @MartinJuhl2

New article published on cross-immunity and protection against SARS-CoV-2 from previous infections

Only 5% of 302 people with a median age of 51 years had cross-reactivity

While 44% (21 out of 48) 1-16 year olds had cross-reactivity with SARS-CoV-2
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https://twitter.com/VirusesImmunity/status/1325085193913462784?s=20

Another new paper just out, contradicts this finding:
Looked at 36 children (1-17 yo) and 168 adults (18-90 yo) finds that pre-pandemic cross-reactive antibodies do not confer protection against infection or disease severity
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https://twitter.com/SCOTTeHENSLEY/status/1326216898812506113?s=20

Overall kids have a significantly milder disease progression, with or without cross immunity

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Two articles from Scotland and Germany show that the more children you have, the less likely you are to end up in the hospital as a result of Covid-19, as well as test positive for Covid-19.
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Sharing a household with children and risk of COVID-19: a study of over 300,000 adults living in healthcare worker households in Scotland
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medrxiv.org/content/10.110…

Association of contact to small children with mild course of COVID-19
Caution, small numbers
Of note, intensive care treatment was reported by three of 19 (16%) inpatients in the child group and by 16/40 inpatients (40%) in the no child group (p=0.056)
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sciencedirect.com/science/articl…

Study that looked at ppl 5 years before the pandemic who had been tested for whether their infection was common cold HCoV's. Does not appear to protect against becoming infected, on the contrary, in turn lower risk of intensive care & lower mortality
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dm5migu4zj3pb.cloudfront.net/manuscripts/14…

Out of 15,928 patients, 875 was previously infected with common cold hCoVs. Of these, 33 were SARS-CoV2 pos subsequently.
Of the 15,053 who had not been infected to previous hCoV's, 437 were subsequently positive for SARS-CoV2.
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Higher proportion of those who had previously been infected with hCoV's ended up in hospital, but there were significantly fewer who ended up in intensive care (ICU) OR 0.1
Follow-up to the study, the difference in %deaths in each group was: eCoV+ (4.8%) vs eCoV- (17.7%).
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A small study which was the first example that cross-reactivity with previous “common cold” HCoV did not appear to confer immunity or mild course in infection with SARS-CoV-2
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medrxiv.org/content/10.110…

Pre-existing T-cell cross-immunity does not indicate, that it will have an effect on the herd immunity threshold
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https://twitter.com/profshanecrotty/status/1313580981341712386?s=20

There are also many places in the world where widespread infection has been seen with up to 40-70% infected overall.
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https://twitter.com/AdamJKucharski/status/1308350331231797248?s=20

Parts of Mumbai tifr.res.in/TSN/article/Mu…
Iquitos researchgate.net/publication/34…
Ecuador academic.oup.com/cid/advance-ar…
Karachi ncbi.nlm.nih.gov/pmc/articles/P…
Ischgl medrxiv.org/content/10.110…
NYC nytimes.com/2020/08/19/nyr…
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~90% of PCR positive was later shown to have antibodies

"Seroprevalence among 195 participants with positive PCR more than 14 days before the study visit ranged from 87·6% (81·1–92·1)"
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thelancet.com/action/showPdf…

Other studies on the importance of T cell response

Article in Nature on the explanation of why women do better than men. It is linked to one's ability to mobilize a good T cell response.

https://twitter.com/VirusesImmunity/status/1298613365657542657?s=20

15/x

The coronavirus is most deadly if you are older and male — new data reveal the risks

"The Man Flu" must therefore be taken seriously - it is now scientific proven
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nature.com/articles/d4158…

Older people have the same antibody response as younger people, so the difference that may explain the difference in mortality may have to be found in T cells, described in this article
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medrxiv.org/content/10.110…

This study looked at the immune response in mild and severe cases. Points to the importance of the trinity of CD4+ and CD8+ T cells as well as neutralizing antibodies work together as part of the adaptive immune system in the early stages
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https://twitter.com/profshanecrotty/status/1306293471817334784?s=20

SARS-CoV-2 memory T cells will likely prove critical for long-term immune protection against COVID-19. We systematically mapped...T cell responses in unexposed individuals, exposed family members, and individuals with acute or convalescent COVID-19
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cell.com/cell/fulltext/…

Good review of the immune response to Covid-19
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https://twitter.com/EricTopol/status/1296935588759629825?s=20

There has been a lot of talk about potentially losing immunity to Covid19 quickly (either through being infected with Covid-19 or potentially through a future vaccine). According to 2 leading experts, they do not think we should be worried about it
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nytimes.com/2020/07/31/opi…

Finally, basic review of how the immune system works
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https://twitter.com/VirusesImmunity/status/1285944893085491204?s=20

Lasting immunity from studying a combination of antibody, memory B cell, CD4+ T cell, and CD8+ T cell memory to SARS-CoV-2 for >6m after infection in 185 ppl

Spike antibody IgG stable >6m
Spike memory B cells 6m >1m
CD4+ & CD8+ T cells T1/2 = 3-5m

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biorxiv.org/content/10.110…

Findings identify low avidity (=accumulated strength of multiple affinities of non-covalent binding interactions) CD4+T cell responses as a hallmark of severe COVID-19, argue against a protective role for CCCoV reactive T cells in SARS-CoV-2 infection
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cell.com/immunity/fullt…