system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If my kids are vaccinated, how are non-vaccinated kids a threat to them?

Just to be clear -- I am 100% pro-vaccination for all children. It has been empirically shown to be more effective than anything else in combating disease (to my limited knowledge, aside from perhaps public sanitation), and the allegation that it causes autism is demonstrably false. I just don't understand why kids who aren't vaccinated are a threat to people who are, and I would appreciate it if someone could kindly explain it to me.
gpt
They aren't a direct threat to your kids. But there is a thing called "herd immunity". Herd immunity is how well a group can deal with an illness, un-vaccinated kids hurt this immunity in two ways.

1 - There are people who cannot be vaccinated. Either because of allergies to something in the vaccine, or a super weak immune system, etc. Having non-vaccinated children that are in contact with this child could get them infected, and since they are so weak the effects of an illness would be more severe, instead of the common cold, it effects them like the flu. The flu could hospitalize them, and in some cases even kill them.

2 - Diseases mutate. This is why there is an annual flu shot and no cure for the common cold, and why things like chicken pox, measles, smallpox and polio are back. When vaccinated people come in contact with the illness, their immune system fights it off, by washing their hands and wearing clean clothes, the disease is stopped then and there. With non-vaccinated people, even if they have a strong immune system and can fight off the illness, they still got it, they still had to fight it and it gave the illness a place to go while it was being fought where it could mutate and potentially become a strain that the vaccine doesn't protect against.