Actually, we do. We here in California have pockets of parents who refuse to vaccinate their kids — to the point where a school full of them starts to lose herd immunity. Within the past twelve months, our governor signed a law significantly tightening the requirements to get an exemption; http://www.mercurynews.com/ci_28407108/gov-jerry-brown-signs... says that only medical exemptions will get you out of vaccinating your kids here in California.