Slippery slopes are logical fallacies, not because they don't sometimes work, they are logical fallacies because they sometimes fail. That being said ...
At what point can the state compel people to have medical procedures done? Pregnant at 15, forced abortion? Take kids away from parents the state doesn't like how they are being raised?
Additionally, THIS kind of ruling / law doesn't really bode well with Abortion. The line is "My body, my choice" is completely done away with.
And what happens when we actually prove that Autism disorder is caused by bad vaccines? We already know some vaccines have really bad adverse problems, and kill. And if Vaccines are completely safe, why do they hide the data regarding adverse reactions with structured settlements?
The fact is, FORCING vaccines doesn't protect ANYONE from ANYTHING. Those people at risk, are still at risk. Those people who have been vaccinated are still protected. In fact, the Measles outbreak at Disneyland had almost nothing to do with the no-vaccine advocates, but was due to a strain that the American Vaccine doesn't fully protected against, and many of the victims were simply too young to have been through the fully regime.
But Facts don't matter when you have government FUD on your side.