Rockland County New York has declared a state of emergency and banned children who are unvaccinated against the measles from public places after a local outbreak enters its 26th week. According to officials the disease was supposed to have been eliminated in the U.S. in 2000. But travelers from other countries and pockets of resident resistance to vaccinations have brought it back with a vengeance. Do those opposed to vaccines pose a health risk to all of us?