Well, I had an MMR booster at 18 years old. I've actually been trying to figure out whether or not an MMR booster is recommended for people who had the 18-year-old one or not. They haven't been talking about this in the news.
@bkuhn@identi.ca in Ontario, there is no MMR booster after age 16 (only the DPT every 10 years). The only reason for a follow-up MMR is if there wasn't a conversion, but that's usually for rubella, not measles, and only in problem cases for which one can be tested.