In the case of Rubella, (At least) Catholic writings treat the vaccination as the lesser of two evils (i.e Passive versus Active cooperation in sin)
In other words:
Yes, abortion is a sin and yes, benefiting from that sin even decades after the fact constitutes passive cooperation.
But,
Since unborn children are extremely vulnerable to Rubella, refusing to have your child vaccinated, would endanger the lives of others and would constitute the active commission of sin should any harm arise from this negligence.
I don't have a dog in this fight either, but do find the thought process interesting.