@NiveusLepus It can vary. I got a COVID booster and a flu shot 3 days ago and didn't feel a thing other soreness, and now a little itchiness, at the injection site. My spouse, same. But one earlier COVID Shot had us both feeling cruddy for a day or two.
Both before and after last week's shots, my more-or-less seasonal asthma ticked up a little. Maybe you've got a bit of that going on, or another of the respiratory viruses humans love to pass around.
@NiveusLepus Correction: the itch is not from the vaccine, it's from the band-aid that covered the injection site. My body, in its wisdom, has decided to develop a sensitivity to the adhesives used in band-aids.🙄