It would probably only take a week of training/practice for someone to get good enough to read them manually. Particularity if the vaccination codes have a common pattern - the same mask, format information and the like. I would expect you can look at a few areas to see if the person is vaccinated (though this wouldn't pick up on someone else's vaccinated status)
We don't need to verify everything though, just extract the vaccinated/not field which is probably in the same location on every QR code (or at least it should be possible to make it in the same area), and maybe the name of the person the QR code is for.
The signature is the whole point of the QR code though, otherwise someone could just trivially create a QR code that has their name and "vaccinated = yes".
