When the measles vaccine was first introduced, the number of measles cases plummeted. But a few years ago, new outbreaks prompted a reevaluation of the vaccine. In some people the immunity had faded after only one dose of the vaccine, so the schedule was changed to include a booster dose.
In 1999 there were only 100 cases of measles in the United States, 71 of them brought in from another country. And now it’s official — as of August 1999, the Centers for Disease Control has declared that measles originating in the United States has been completely eliminated!