THAT is not proven at all. In fact, for this class of viruses, it would be exceedingly unusual.
Why?
In very brief & simplified terms:
1) The rapid and extensive mutations.
2) Covid rarely kills directly by itself. As with Flu, it's the complications that can get you. Case in point: My brother almost died of necrotic pneumonia brought on by flu. Is he now immune to flu for many years? Are you kidding?
who says it’s is truly rapidly mutating? ONLY those who want the public to believe it is some new virus and super deadly and mutating super fast.
I think the gene therapy spike proteing crap is what is helping spread whatever the illness is.
with literally hundreds of corona viruses existing before this thing came on the scene, and the fact most of 2020 and 2021 the tests could be altered to amplify sample from any similar corona virus and home test kits could be designed to test positive for more then one type corona virus or have it in the kit already so anyone with runny nose snot or not,twists a “test” swab - good likely hood most people had some version of excisting corona virus or flu.
the spike protein crap not only killing and harming many, likely isn’t good for unvaxxed to be around long periods of time without them being immunally weakened in some way.
#2 rarely kills by itself? even italy when it cut out 3/4 of it’s deathwith covid to become death by covid number was still a sizable chunk of people to have died from whatever covid is, so it’s not rare.
there are various flus so no, but your brother is likely immune to that flu. Just as when you survive one corona virus you no longer catch that one but one of the hundreds of others always circulating the earth various places & times of the year.
Not kidding, your brother’s immune system will be able to fight off the strain of flu virus that made him sick the first time.