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discovered that certain types of cells in blood samples taken from donors in 2015-2018—well before COVID-19 arose—were reactive against the COVID-19 virus. In other words, those blood samples were at least partially immune from the coronavirus even though they had never been exposed to it.
"CD4+ T cell responses were detected in 40-60% of unexposed individuals. This may be reflective of some degree of crossreactive, preexisting immunity to SARS- CoV-2 in some, but not all, individuals," the researchers state in the paper
Whether this immunity is relevant in influencing clinical outcomes is unknown—and cannot be known without T cell measurements before and after SARS-CoV-2 infection of individuals—but it is tempting to speculate that the crossreactive CD4+ T cells may be of value in protective immunity, based on SARS mouse models (Zhao et al., 2016). Clear identification of the crossreactive peptides, and their sequence homology relation to other coronaviruses, requires deconvolution of the positive peptide pools, which is not feasible with the cell numbers presently available, and time frame of the present study.
Scientists estimate herd immunity for the coronavirus is reached when 70-90% of the population becomes immune to a virus, either by becoming infected or getting a protective vaccine.
Despite its relaxed response, Sweden is nowhere near to hitting that goal. Tests on 1,118 Stockholm residents carried out by Sweden's Public Health Agency over one week in late April showed that only 7.3% had developed the antibodies needed to stave off the disease.
Understanding adaptive immunity to SARS-CoV-2 is important for vaccine development, interpreting coronavirus disease 2019 (COVID-19) pathogenesis, a
it is tempting to speculate that the crossreactive CD4+ T cells may be of value in protective immunity,
Because the new virus retained the neuraminidase (N) antigen N2, persons who had been exposed to the 1957 virus apparently retained immune protection against the 1968 virus. This would explain the mildness of the 1968 outbreak relative to the pandemic of 1918–19.
originally posted by: Phage
a reply to: highvein
What's Norway doing?
Do you mean Sweden? Things aren't going that great in Sweden.
Well I’ll go with history. Herd immunity is pretty much the way mother nature has dealt with viruses throughout history .
I wonder what would make Sweden so special.
That kind of shows that more people are immune to it.
And other things, like antibody tests. But you didn't read it , did you?
Your links use death rates to confirmed cases.