Then go ahead and vaccinate your grand kid with MMR .. I had the mumps, every kid born in the 50's had the mumps, I never met or knew a single case that caused anything more than bed rest for 3 days. But I can give you 100 phone numbers of moms and dads that say their kid was absolutely fine until the MMR shot, let the parents decide. Funny thing until the mid eighties this wasn't really a problem, same time frame as the MMR shot ... call me silly