Two of the three of my children got whooping cough even though they received the shot to protect them from it,66% not very good protection if you ask me.
Then again they don't have smallpox
I am old enough to remember childhood illnesses sweeping through our school and every kid getting everything--measles, chicken pox, mumps, whooping cough. We got it all, because there were no shots for those yet. It was common for kids to lose weeks of school every year in waves. My daughter and her friends have never had any of the things that we all got.
But not polio or smallpox! They already were vaccinating us for those. In the 60s and 70s it was unthinkable to not get your kids vaccinated-- they did it at school and everyone lined up and got them. I think there were one or two kids in the school who had letters from home saying they were not to get the shots. We did not know why, but it was probably religious. Certainly not due to any stupid movie star--with no science or medical background-- saying they were not sure the shots were safe.
Vaccines are not 100% effective, if the disease is around. That would be like never being exposed to the disease at all. Clearly your kids were exposed to the disease. If they had not been vaccinated, and then were exposed, they all would have gotten sick, and probably much sicker than they were. (Depends on how bad the case was--I am assuming and hoping that they were okay.)
Vaccines are not only about individual protection, although they have to be marketed that way to make sure enough people get them.
Vaccines are about statistics and critical mass.
Some people who are exposed will get sick, not matter how many people get vaccinated. But they will be less sick, and far fewer people will get sick than if nobody was vaccinated. Eventually, so few people in the population are getting really sick that the disease germs don't reach a critical mass and die out due to lack of hosts to spread it around.
If enough people in a population are vaccinated, the disease dies out that much quicker. But some diseases, like the flu, change every season instead of completely dying out, so we have to keep on getting the shots.
This is my lay person understanding, anyway.