Go to an old cemetary and witness all the baby graves from before the 1950s & 1960s. After that you hardly find any. That's when people started vaccinating their kids. If you're unsure about whether to vaccinate your kids, the answer is literally written in stone. Vaccines work.
For me, it's growing up with all the old men with wasted limbs from polio. The vaccine meant that fear didn't exist in my generation.
I remember as a kid getting in the long line with my parents to take the new oral polio vaccine when it became available for the masses. Sad for me is remembering one girlfriend in college had a shorter leg due to polio.