Thread by @PSampathkumarMD

Cross reactive immunity to COVID?

Several studies now suggest that T cells reactive to COVID may be present even in persons without prior exposure to SARS CoV-2 suggesting presence of cross reactive immunity presumably from prior corona virus infections.

Thread with links
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La Jolla: 40-60% samples from persons with no prior exposure to COVID had T cell responses. @CellPressNews
cell.com/cell/fulltext/…

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Netherlands: 2 of 10 healthy controls with no prior exposure to COVID had evidence of reactive T cells.

immunology.sciencemag.org/content/5/48/e…

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Karolinska: Twice as many close family contacts of COVID patients had memory T cells against SARS CoV-2 compared to antibodies. biorxiv.org/content/10.110…

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Germany: Cross-reactive SARS-CoV-2 T-cell epitopes revealed preexisting T-cell responses seem in 81% of unexposed individuals, and validation of similarity to common cold human coronaviruses.

researchsquare.com/article/rs-353…

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Singapore: Samples from patients with the original 2003
SARS had T cells reactive to SARS CoV-2.

biorxiv.org/content/10.110…

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These studies raise the question whether seroprevalence studies underestimate the proportion of the population that has some degree of immunity against COVID

We dont know if these T cell responses are protective and for how long. We still need to continue all the precautions
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But they may partially explain the rapid decrease in cases in many hotspots despite low levels of seroprevalence.

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Is cross reactive immunity the reason why in the Antarctica cruise ship report, we had 10 rooms with 2 passengers each, in which one had COVID and one didn’t despite 20-30 days of close contact? thorax.bmj.com/content/early/…

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