Building an Immunity Fence against Measles

In "Mending Wall," Robert Frost quotes his neighbor as saying "Good fences make good neighbors" [1]. Since 1966, the United States has been building fences of immunity against measles to stop the spread of the virus within and between communities and to prevent introduction of the virus from other countries, with reestablishment of indigenous transmission [2, 3]. The building blocks in this fence are each susceptible individual rendered immune through vaccination with measles vaccines, which were first licensed in 1963 [4]. The health burden of measles in the United States prior to vaccine licensure was substantial. Over 500,000 cases were reported annually, there were probably -,4 million cases that occurred each year, and these cases were associated with 48,000 hospitalizations, 4000 cases of encephalitis, and 500 deaths [5]. Measles vaccines offered the opportunity to eliminate this burden. The declaration, in 2000, that measles was no longer an endemic disease in the United States represents the achievement of a 34-year effort, characterized by several cycles of marked reduction of disease that were the result of vaccination fol-