This graph shows the number of reported measles cases per year in the United States. Actual cases were likely much higher: Alexander Langmuir estimated that about 4 million measles cases occurred in each year shortly before vaccine introduction (Langmuir AD. Medical importance of measles. Am J Dis Child 1962;103:54-56). Note the drop in cases after the introduction of the first measles vaccine in the early 1960s. Source: CDC/MMWR Summary of Notifiable Diseases, United States, 1993; CDC/MMWR Summary of Notifiable Diseases, United States, 2008.