I think that really goes without saying - I mean, my kids have all had the chicken pox vaccine, but that doesn't mean that I am going to allow them to be exposed to it just because they are vaccinated. Same for measles, mumps, rubella and all the other things they have been vaccinated against. The trouble is, most people pass on these things before they have even realised they are sick - for example, chicken pox is most contagious in the stage before the spots appear. Most people don't even have an inkling that they might have it until then, by which stage they could have potentially passed it on to lots of people without even realising. Whooping cough is also contagious before the person has even realised they might be sick, seen a doctor and been diagnosed - which is why often when someone is diagnosed, they medicate the whole family with antibiotics, or at least test everyone. At least if you have been vaccinated, you have a level of protection against these things.

And vaccinating does provide a greater level of protection - nobody can guarantee 100% that you will not get a disease after you have been vaccinated against it, but it is highly likely that if you DO catch it, it will be in a very mild form and your immune system will kick into gear and start fighting it a lot sooner - meaning that you are also less likely to pass it on (although the risk is still there of course).