With recent outbreaks of measles, pertussis, and even polio across the United States, I think it's time to revisit our laws about vaccination.
Refusing to vaccinate your children doesn't simply put them at risk: it puts at risk everyone who, for medical reasons -- extreme youth, old age, health, allergy -- can't be vaccinated, as well as everyone whose vaccinations have lost potency over time. Personal objections to vaccination, whether it be because of (unsubstantiated) fears of side effects or religious reasons, put everyone around you at risk of death or serious injury. This is a classic case where your right to swing your fists around ends at my nose: the individual liberty interest in allowing people to decide which medical procedures to undertake is outweighed by the safety and survival interest of those around you.
I believe that it is time to end all non-medical exemptions from critical vaccination requirements such as MMR, DTaP, and polio -- for epidemic diseases which kill and maim by the thousands when our immunity, as a population, is compromised.
My preference would be to treat this as a criminal matter: to fail to do this amounts to reckless endangerment. (Public endangerment, that is, not simply endangerment of a minor) More important, however, is the prevention of harm from people who do this: in particular, individuals unvaccinated without medical reason should be barred from all public accommodations where their presence could put other lives at risk, including schools, parks, pools, and transit.
Such a barring would, of course, have a nearly-catastrophic effect on the life of anyone not living in a remote, rural area; it essentially would reduce a person to second-class citizenship. However, I believe that this is a reasonable accommodation of the public safety interest, as by definition it is something which the person can circumvent by simply not putting the general public in danger by their mere presence.
There are times when I'm willing to be fairly forgiving. When the rightness of a course of action is unclear, I'm generally in favor of letting said action be a matter of individual conscience. However, when an individual's actions put those around them at risk, this is exactly what we have laws for. You have no more personal right to expose others to deadly diseases than you do to fire a gun blindly into the street.