warning sign

In light of this news story:

"There has been an upsurge of measles cases in the United States, mostly because of parents’ misguided fears of vaccinations."

When I Become King ... any child who has not been vaccinated due to their parents' choice will be forced to get a tattoo in a prominent place on their body, to serve as a warning to others that their mere presence could be fatal to their sane-parent classmates.

I'm thinking something subtle - like a yellow "Star of David" in the middle of their forehead.