Of course that's how it works. We don't regularly administer small pox vaccines anymore because it has been eradicated except for a couple of very tightly controlled samples. That's what "eradication" means. My memory is slightly hazy, but I think we might have skipped Polio as well for anyone not going oversees, because Polio largely meets the definition of "eradicated" in the US. Meanwhile, we continue to administer MMR and Chickenpox vaccines because those diseases still exist in the wild. The very fact that Measles has returned is ipso facto proof that it was never eradicated, and the fact that (normal) people never stopped giving that vaccine to their kids is proof that no one ever believed it was.