vaccines aren't like an antidote in a movie, or something. this isn't superman.
a vaccine, if targeted, might help protect certain vulnerable groups in the sense that it would reduce the likelihood of acquiring the virus, but you have to look at these numbers carefully. we know this virus is very contagious. so, if we estimate that you have a 90% chance of catching it if exposed to it, and the vaccine has a 60% success rate in stimulating antibodies (about on par with the flu), the chances of a vaccine protecting you are .9*.6 = 54%.
that is risk reduction, clearly.
but, you wanted better numbers than that, didn't you?
the tricky thing is that the virus is so weak, and i've admitted that i've had to walk myself back a little - one of the few things i've walked myself back on. because the virus is so weak, it doesn't always produce an immune response. what that means is that you should expect it to be one of the least effective vaccines we've ever created, because it's one of the weakest viruses we've ever tried to vaccinate against.
if you're old, you should get vaccinated. don't misunderstand me.
but, there is no real way around the reality that we have to let this circulate in order to beat it.