This is the responsibility of all of us, isn't it? I think we have to try persuasion with anti-vaxxers, one person at a time. Patiently and kindly or something. We know and insulting won't work, so just patiently explaining, emphasising the problems in the reasoning behind their stance etc. Threads here are quite good for that and I'm sure there's other SM where the same thing happens. One step at a time.
I don't think vaccinations should be mandatory for the reasons hercule has outlined, though I very much support the herd immunity thing and think vaccines are a brilliant medical discovery.
It's one of those things where society as a whole has to take a stance - a bit like shunning absent fathers who won't pay for their children (I know that doesn't happen atm, but I live in hope).
Eventually it becomes socially unacceptable not to be vaccinated, a bit like smoking; anti-smoking feeling in a large proportion of our population was helped by the ban, of course.
I think that my daughter's generation, as a whole, are more sensible about vaccinations. There are a few exceptions, obviously, but children will remember how awful it was when measles ran rampant through their nursery, or when their friend died from it or became brain damaged etc. I think, sadly, that it will take another epidemic and some very serious consequences before the current generation of anti-vaxxers start to rethink their stance.