This fully explains the wild divergence in outcomes even among similarly-morbid people. The more "matches" you have on a pre-existing basis the more-fully your immune system can recognize the virus and while you will get infected if those matches are among the nucleocapsid section you're much more-likely to drive it off without serious consequence.
Note that among the "PRE" (not-infected) collection of samples all were prior to November of 2019 and thus presumed non-infected. We in fact know there were infections during that time frame but most in that group were from wildly before Covid-19 by as much as 10 years or more, so the cross-contamination percentage is going to be very low.
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[Of the SARS donors, 100% showed T cell responses to cross-reactive and/or specific ECs (HLA class I 86%, HLA-DR 100%; Fig. 5d,e), whereas 81% of PRE donors showed HLA class I (16%) and/or HLA-DR (77%) T cell responses to cross-reactive ECs (Fig. 5d).]
81% eh? Isn't that an interesting number? Where have we seen that before?
You know damn well where, don't you?
It's the rough percentage of alleged Covid-19 infections that were either asymptomatic or very low-symptom for which no medical treatment was sought and, in many cases, not detected.
So it wasn't 30 or 50% who had pre-existing protection it's actually roughly 8 in 10! This was not a "novel, everyone is susceptible" virus at all. It never was. You were lied to from the very beginning and thus all the "models" based on that were trash.
[Taken together, SARS-CoV-2 T cell epitopes enabled detection of post-infectious T cell immunity in 100% of individuals convalescing from COVID-19 and revealed pre-existing T cell responses in 81% of unexposed individuals.]
Now we know why Diamond Princess happened the way it did. It was never possible for more than 20% of the people on that ship to get seriously-symptomatic Covid-19 despite being cooped up in close quarters for weeks with an aerosol-spread disease and cruise passengers generally being wildly-overrepresented for various morbidity factors.
It also completely explains why one of two people quarantined in the same cabin got sick and the other did not.
In 100% of the persons who had and recovered from Covid-19 and 81% of those who have never had the virus a vaccine may well be worthless as they already have T-cell response.
While this will not prevent them from getting it again there is questionable at best benefit over their existing immunological state but there is risk, including a risk of death, from the side effects.
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[Furthermore, evidence was provided for a lower recognition frequency of cross-reactive HLA-DR EC in hospitalized patients compared to donors with mild COVID-19 course, which might suggest a lack of pre-existing SARS-CoV-2 T cells in severely ill patients.]
[Our observation that intensity of T cell responses and recognition rate of T cell epitopes was significantly higher in convalescent patients compared to unexposed individuals suggests that not only expansion, but also a spread of SARS-CoV-2 T cell response diversity occurs upon active infection.]
Again for those who are reading-comprehension challenged: The existing vaccines are worthless for building said perfected immunity since the data is that the nucleocapsid section, which the vaccines do not code, is where most of the pre-existing resistance against serious disease resides.
What we are doing now is encouraging more-contagious mutation and if we don't cut it out we may well pull the black ball and get the more-virulent mutation as well that will evade all those who are vaccinated and hammer the hell out of them since none got any nucleocapsid T-cell recognition from the shot!
If that happens those without said existing recognition are very likely to die; we could easily wind up killing 20% of those vaccinated because we were stupid.
THIS MUST STOP NOW.
I am not anti-vaccination; to the contrary, vaccines are one of a handful of clear medical triumphs.
I am anti-stupid, and producing, promoting and injecting people with something you do not yet understand the pathology of, taking your information from a potentially-hostile nation and not performing scientific verification first is stupid.
To continue said activity in the face of science documenting that you did it wrong goes beyond the realm of stupid and into the realm of criminal culpability for which no immunity should be recognized by anyone, ever, period.
And for the Love of God stop masking and restricting young and healthy people; the future of the world in terms of public health in fact requires that they be allowed to develop said natural, perfected immunity.
Preventing that by giving them a shot is felonious and anyone involved in it should be indicted, prosecuted and lose their life as the mass-murderers they will prove to be.
Link to Study --SARS-CoV-2-derived peptides define heterologous and COVID-19-induced T cell recognition :
https://www.nature.com/articles/s41590-020-00808-x.pdf