Who's talking about genetics? This is about antibodies! It's not looking at the DNA of the immunized person. At all. It's not genetics. It's identifying the specific chemical results of their immunication, not the person. At all.
Do people not understand that? This is a ridiculous digression from the subject at hand, just to talk about some kind of Sci-Fi fantasy dystopia?
Welcome to Hacker News. I guarantee you almost no one bothered to read past the words "blood marker" in the title. You can tell because the article has pop-ups and no one is ranting about them.
But I don't think it's such a ridiculous digression from the subject at hand - The original article was just a "water is wet" study saying that the more antibodies you have floating around in your blood the better able you are to fight off a virus. When you have that kind of article people will naturally digress in their discussions. And with COVID, dystopia is never far off-topic. (Just depends on your politics whether you see it more like V for Vendetta, or more like Pandemic or maybe Omega Man.)