[PorscheGAL]

You could easily go to your doctor and get a titer to check your immunity level. Most insurance pays for it.

As for people upset: 5-10% of vaccinated people's body do not process the vaccine the same as others and they will have no immunity. Measles is caused by a virus and viruses can mutate. The more people who are passing it around, the more likely there is a mutation that will not be affected by the vaccine.