1) Flu shots dont go into the viens... they go intramuscular, usually in the delts..unless itsa mist which would be inhaled nasally
2) docs and nurses simply draw the vaccine from a vile into a syringe and inject... they have no idea where the vile came from and rely completely on the series of checks that the manufacturer does or does not do on the viles. Mistakes have been made in the past where people have been injected with the virus and not the vaccine.
3) The data base is not as complicated as it would seem. it could be set up "as we go".
4) What training?