Suppose someone has COVID-like symptoms. Let's pick an arbitrary date; say they wake up coughing on February 1st, 2022, with no prior symptoms, and unknown potential exposure date.

If this person is unable to find any COVID testing until February 7th, 2022, how reliable will the test be in determining if they had COVID, as opposed to, for instance, the flu?

How about February 14? 21?

Are there some types of tests that will be more reliable for days "1 through N" vs. "N through M"?

NOTE: this question is different from "how long after infection is the earliest you should be tested", which the Internet seems to be obsessed with.


1 Answer 1


Antibody tests can identify prior infection for at least several months after acute infection, but more than that is unknown.

Vaccination produces antibodies against the S protein; testing for antibodies against the N protein (the nucleocapsid) can distinguish between infection and vaccination.


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