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Before you were vaccinated you could have donated blood and they would have tested for antibodies. A possible indication, but not something that would confirm it is if you had a reaction to the first shot. A number of folks I know who had covid had a more serious reaction to the first dose.

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I had separate exposure to COVID-19 before vaccination, and before it was super easy to get tested for antibodies. The reality is, whether or not I had exposure or not hardly matters at this point, and it's impossible to prove one way or the other.

It may be very hard to determine if people sick in 2019 had COVID-19 or something else at this time.

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