I'm no expert on the biology. But AFAIK there's no _universal_ contamination source that would be screwing up all these tests, as they're various forms of antib

I'm no expert on the biology. But AFAIK there's no _universal_ contamination source that would be screwing up all these tests, as they're various forms of antibody reactivity tests. This isn't like PCR testing where trace amounts of the virus cause false positives. OTOH, as I said, it certainly doesn't prove by itself that the antibodies came from COVID infections.