My kids are vaccinated, I just don’t see why others should be forced to do something to their children that they don’t agree with. Their kids shouldn’t be kept prisoner either obviously.
Ok, so imagine your kids WEREN'T vaccinated, even though you (as a sensible, thinking individual) want them to be...
This could be for a couple of reasons:
Your kid is immunocompromised (for any one of a variety of reasons)
The vaccine simply doesn't work for your child (happens to a certain % of kids)
Along comes kid B, whose parents, in their infinite wisdom, decided not to vaccinate their child. In fact, they and a bunch of their friends decided the same thing, because they watched a video on youtube you see, and that Jenny McCarthy lady seemed ever so kind and sincere...
Now one of these kids - someone your child doesn't know and has never met - has been on holiday recently. Lovely it was. 3 weeks in the Dominican Republic. Unfortunately while there, he picked up a bit of a cold. Nothing too serious, didn't even spoil the holiday. Came home and went right back to school. Week or so later, his friend (who's in your kid's class by the way) has a bit of a cold too. He stayed off school for a few days and was fine.
Problem is, it wasn't a cold, it was diphtheria, which in some people only shows up as a bit of a cold and they get over it no problem. The rest of your kid's class had their vaccinations and don't even get those symptoms.
You child, on the other hand becomes very sick. They develop a high temperature, feel really sick and their neck becomes visibly swollen. They have terrible trouble swallowing and you take them to the doctor. Now there's treatments available, but with your child's lack of immunity, it takes a while before the treatments work. The doctors eventually get things under control (unlike the ~10% of kids who die even with treatment), but your child is left with permanent damage to his heart muscle and kidneys.
Now obviously this is a very specific (and perhaps severe, but by no means impossible) example.
Vaccination (and the choice to do or not) is about more than the individual child. A certain % of children RELY on herd immunity to stay healthy.