It used to be a concern. Vaccination stopped that. Vaccination will continue to keep it stopped only so long as people use it.
Only one disease has ever been completly eradicated from the wild. Polio has been tantalisingly close for years too, but a different strain of anti-vax has been hindering eradication. Measles, however, is still there... simmering. Just waiting for the chance to make a resurgence.