What's the difference between immunization and vaccination?

My understanding is that an immunization means you have protection of something ongoing once you get that. Examples are measle, mumps, rubella immunizations. If you have that you do NOT need to get that ever again and should be able to avoid those illnesses then. A vaccine is something less long term in the effect, like the flu vaccine. They have to offer it every year as the strain of flu is different they claim and the prior vaccine against it may likely not protect against it.