It’s too late by then. The point of a vaccine is to show your body the antigen so it has a head start in preparing its defenses against that pathogen. If you’re already infected, then you have to hope your body can defend itself. Otherwise, your only shot is monoclonal antibody therapy, like what President Trump got in the hospital. But that’s not a silver bullet.
The vaccines have to be given in advance of you being exposed. After does you no good.
I actually said it in jest, because just another fake news push to get people to take the death jab. 8>)