From nbc news World Headquarters in new york this is nbc nightly news with brian williams. Good evening. It was thought to have been eradicated in the United States but now measles is making a comeback. And just tonight the centers for Disease Control issued a wakeup call to all of us. Public Health Officials are treating the return of measles. This outbreak very seriously. It has now spread to over a dozen of our 50 states including the state of arizona where they fear upwards of 1,000 people may have been exposed. This of course as thousands more are arriving there for the super bowl. This also brings sharp attention to the issue of vaccinating our children. Its where we begin tonight with nbcs Hallie Jackson in phoenix. Hallie good evening. Reporter good evening, brian. Officials say its not that the measles vaccine isnt working, its that its not being used. The cdc describe ths outbreak as a wakeup call and here in phoenix theyre listening. At this childrens clinic signs warn a run