I wasn't going to jump into this conversation, but I want to add another dimension to the discussion of the benefits vs. dangers of vaccinating. I feel qualified by the fact that my first-born child had a severe reaction to her first DPT vaccination many years ago.
We got her first vaccination on time when she was two months old. Within ten minutes, she was screeching non-stop, like a threatened animal. We got sent home anyway, where she continued to screech for many hours until she had a seizure and went into a coma for three days. Happily, she woke up and seemed perfectly fine. She didn't have any long term neurological damage.