Might want to research a bit more on 'historical vaccines', whatever that is. Measles vaccination comes with breakthrough infections, as does the annual influenza vaccine.
To your other point, so because you can't GUARANTEE an outcome, there really isn't any reason to employ a strategy? I shouldn't have to point out how ridiculous this notion is, but I'll try with an example:
A car hitting a child at 20 mph can and has caused injury and death. Clearly going 20 mph in a school zone does not guarantee a safe outcome. So why do we have school zones? Why don't we just drive 60 everywhere?