The problem is herd immunity. If you're okay with getting sick and you opt not to get vaccinated, whatever. You can get sick. The problem is that by getting sick you are now able to spread your affliction onto others, and you're compromising herd immunity.
If enough people get vaccinated, it protects the unvaccinated people as well by stopping the spread of disease. So each person who withholds vaccination increases the chance that the disease will be able to spread and reach all the unvaccinated.
EDIT: To give a more simple example, do you think it's okay for people to show up to work badly ill with the Flu or some other transmissible disease? What if they get the whole team sick? Is that okay?
To me vaccines provide enough individual benefit that there is no need for a social solution. Vaccines are not a case of market failure.
Especially in the United States it strikes me as insane that vaccine manufactures are by law not liable for the side effects of vaccines, yet people would propose to hold individual parents liable for not vaccinating their children. (Note: I'm not talking about crazy autism stuff, but the risks that have been proven and for which industry has sought protection)
Ignoring for the moment how totally insane our legal system is, I think it's very debatable it's the right tool to deal with side effects.
The thing is, we know there are going to be side effects, some severe, some fatal. The government licenses these vaccines knowing, statistically, that X number of people will get sick, Y crippled, Z killed. But it does this because the alternative is far worse. So as long as it's not stingy, it makes sense for it to run a system (http://en.wikipedia.org/wiki/Vaccine_court) to pay out to those families affected, rather than the capricious legal system that won't compensate a lot of people.
As I've noted elsewhere, expose manufacturers to unlimited liability and we eventually won't have any left. We were in fact almost there when the compensation system was changed.
Also, you may not be talking about "crazy autism stuff", but lawyers certainly were and would be if set loose again.
To me the benefits of herd immunity dramatically outweigh the consequences of minor side effects from vaccines. The immunocompromised have few options other than to rely on the rest of us to get vaccinated.
If enough people get vaccinated, it protects the unvaccinated people as well by stopping the spread of disease. So each person who withholds vaccination increases the chance that the disease will be able to spread and reach all the unvaccinated.
EDIT: To give a more simple example, do you think it's okay for people to show up to work badly ill with the Flu or some other transmissible disease? What if they get the whole team sick? Is that okay?