But, those born between 1957 and 1989 may have received only one dose of measles vaccine. A single dose was recommended from 1963, when the vaccine was introduced, until 1989, when it changed to two doses. People in this group may benefit from a second dose depending on their age; risk factors; occupational exposures, such as working in health care; and travel plans.
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https://med.stanford.edu/news/insights/2026/01/measles-in-america--five-things-to-know-from-a-stanford-medicine.html