narrator: marianna fastovsky has four children. she vaccinated at first, but then one child had a seizure. fastovsky: i'm just really worried about reactions. and i am worried about the diseases. so i'm kind of confused, really. narrator: in america, children must be vaccinated before they start kindergarten. but the required shots vary from state to state, and most allow for exemptions based on personal or religious beliefs. here in california, almost three percent of children are exempt, and in some schools it's more than 30%. i have a lot of friends who don't vaccinate at all, and if you say "vaccine" around them, they look at you like you are literally, well, you know, like you were poisoning" your child., on the other hand, you have parents that they can't even understand why this is even a question. makstman: nobody is willing to really have a conversation with you and discuss what's a severe reaction, is it okay to have a seizure... i would really like to know what the real risks are. brian zikmun-fisher: is it okay to quest