I think you wandered into the wrong forum...and the wrond thread. OP clearly states in her post she is looking for support. To tell a mom who is worried about the life of her baby that her choices were irrational and she possible could have prevented this is not supoortive and incredible insensitive. I see you are a med student. I hope you treat your future patients with more respect.
So in interest of full disclosure: I'm an atheist. I'm highly pro-vaccine.
Response: What a horrible situation. I hope you find more support in the days ahead. Of course you feel guilty! What normal human wouldn't? You love your child and in retrospect (where everything is too clear too late) you may have had the opportunity to prevent this. The what-if game is insidious. I'm of the personal opinion that your decisions were irrational BUT the point is at the time you decided to not vaccinate you were doing so for caring reasons. In psychology they talk about "good enough parenting". You don't need to be perfect, you just need to be good enough. And now it seems like you are already rethinking your vaccination approach for the same reason you didn't vaccinate: out of concern for your child. I hope your kid pulls through.