Good question. If it is like your typical flu vaccine then it may not very effective. It is probably not a good analogy but efficacy of the flu vaccine is usually around 40% because it is a guess when they create the vaccine and the actual virus may have mutated by the time the vaccine is in wide distribution.
It is a calculated roll of the dice.
Your 40% might actually be a good guess.. I "think" I remember reading an article last year that researchers said that the COVID virus was not "mutating" like most viruses, so a vaccine would be possible ...now of course they are saying it is mutating ..... IF this is indeed a man made virus (which I believe it is) No one really knows where this might go, but right now recovery rate is 99.97% .
I am old with COPD so my daughter made a vaccine appointment for me and even had her brother come to take me (because I had no intention of getting one), and I have no intention of a booster ...