Should states require all parents to immunize their children?

To vaccinate, or not to vaccinate? That is increasingly the question for American parents, some of whom believe mandatory childhood vaccinations may harm their kids. All but two states allow parents to opt out based on religious grounds, leading some parents to lie about why they're not vaccinating their children. But vaccine advocates argue that fears about the adverse effects of vaccinations -- particularly their link to autism -- are scientifically invalid. They also point out that parents who don't vaccinate their children put other kids at risk. Unvaccinated kids can still contract and spread illnesses to vaccinated but vulnerable children or to those too young to have received vaccinations yet. Do parents need a reason not to immunize their children? Tell us what you think!