自1963年麻疹活疫苗在美国使用以来,报告的麻疹发病率明显下降。应用一个剂量的麻疹疫苗就可获得较高的免疫水平,但是麻疹爆发仍时有发生。据观察,麻疹目前有两种主要的流行形式:一种爆发主要发生在城市内未接种疫苗的学龄前儿童,另一种爆发发生在高免疫接种的中等学校和学院人群中。1980～1989年间爆发多发生在中等学校,每年发生在大学校园的病例只占全部病例的 Since the measles vaccine was used in the United States in 1963, the reported incidence of measles has dropped significantly. A higher dose of measles vaccine can be used to obtain a higher level of immunity, but measles outbreaks still occur. It is observed that there are currently two major forms of measles epidemics: one in pre-school age, where the outbreak occurs mainly in the city and the other in high-immunization secondary school and college populations. Between 1980 and 1989, the outbreak occurred mostly in secondary schools, and the annual incidence on university campuses only accounted for the total number of cases