Is 21% plausible? Sure. Is it certain? Nope.
We need to know more about the methodology:
Is testing 3k people at supermarkets a biased (non-representative) sample? Likely, in some sense...
PLUS, just because a test detected antibodies, it does NOT mean that all of these people are immune.
Ok, so what does this mean then?
It means the virus is STILL spreading in NYC.
It means that the MAJORITY of us are still very susceptible!
It means we still need to #StayHome.