Should vaccinations be mandatory? Should you be forced to inject something into your body, against your will? Because that's what 'mandatory' means; eventually they would come looking for you and force you to take the vaccine.
It's just not feasible to make vaccines mandatory and I'm saying that as a pro-vaccine advocate.
What is possible, is to ban unvaccinated kids from schools (with the exception of medical exemption). An anti-vaccine parent would have to home-school their kids, or send them to some special (preferably non-government funded) school.