Regardless, most vaccine sites collected your insurance info and entered the data there so it should be in your records.

Anecdotally, I've heard of some vaccination sites in the early days that didn't bother, and there's always the possibility of errors.

But even so a legit vaccine card should be able to be verified as appearing to be legit and consistent with the vaccine site, batch numbers, signature, etc. Also thing like appointment calendars, emails, etc can help verify.

A fake card would likely be very easy to verify as fake if you went to the trouble... vaccination site didn't exist, dates wrong, batch numbers wrong or more likely totally invalid, signatures can't be reconciled with a real provider, etc.

But you'd have to be pretty stupid to quit your old job and take a new one planning to rely on a cheap fake document... that's on par with showing up with a fake 1C medical. UAL is better off without them. Assuming it's even true and there's anybody actually that stoopid.