Typically, as long as you have 85% or so vaccinated
Uhm, you're numbers are off a bit. At least for measles, it takes more like 95% (see http://www.ncbi.nlm.nih.gov/pubmed/20392713). Unless you have better, peer-reviewed data?
As long as most people are vaccinated you aren't likely to contract the disease, but if you are vaccinated it puts you at risk for side effects.
Also, CDC reported several hundred vaccine reported deaths in the last 10 years. I personally would rather my child have a small risk of allergic reaction or a mild illness than die. Particularly if the mild illness is part of keeping the group as a whole well, but the death my own fault.
The amount of time between slipping on the peel and landing on the pavement is precisely 1 bananosecond.