My SIL comes from an anti-vax family. He defied all his upbringing and had the vaccine anyway. My daughter had to take him to hospital afterwards - panic attack.

Some people genuinely can't take it, but I think it's overstated / misinterpreted how many.

I myself had mild non-allergic reactions to 2 of the 4 shots I've had. The first Astrazenica shot was the worst, with 2 days off work, but I chalk it up to an immune response to a new pathogen. Exactly what it's supposed to be doing. 2nd AZ shot - nothing, then Pfizer, reaction again, though much milder.

I recently had an allergic reaction to a common drug. Very different experience.

I have not had COVID.

Edit: That is to say, both things are responses but an anaphylaxic reaction is not the same as an anti-body reaction.

https://pch.health.wa.gov.au/For-health-professionals/Emergency-Department-Guidelines/Anaphylaxis