Measles causes birth defects in unborn children if their mothers get it.
Mumps can make boys sterile.
Of my first cousins (Male) over 55 we have 38 kids, we all had the mumps, with a high of 8 and a low of 2, I don't think that to many blanks were shot.
The problem lies in getting measles as an adult, key word adult, why do you get measles as an adult, when it is threatening, no exposure as a child, Occam's Razor.
I don't advocate not getting shot up but look what happened to the poor Aztec Cannibals, when civilization falls and you are exposed to a new disease vector, measles.