A vaccine prepared from live strains of the measles virus. It is the preferred form except in patients who have one of the following: lymphoma, leukemia, or other generalized malignancy; radiation therapy; pregnancy; active tuberculosis; egg sensitivity; prolonged treatment with drugs that suppress the immune response (i.e., corticosteroids or antimetabolites); or administration of gamma globulin, blood, or plasma. Those persons should be given immune globulin immediately following exposure.