BOX 4-1 Alaskan Measles Outbreak in 1998 In late 1998 an outbreak of 33 confirmed measles cases (ages ranging from 2 to 28 years) occurred in Anchorage, Alaska, including 17 cases among a highly vaccinated high school population (CDC, 1999g). Analysis of the outbreak revealed that Alaskan schools did not require students entering kindergarten or first grade to have two doses of MMR until September 1996. Consequently, in the high school setting of 2,186 students, about half (1,057 students, or 49 percent) had received one dose of MMR, and the remaining half (1,112 students, or 51 percent) had received two or more doses (only 1 of the students had not received at least one dose of MMR before the outbreak). The Alaskan Department of Health and Social Services issued an emergency order requiring all Anchorage schoolchildren to have two doses of MMR by early January 1999. By mid-November 1998, 98.6 percent of the almost 50,000 Anchorage students were able to produce such documentation. Although no endemic measles virus is currently circulating in the United States (the outbreak was traced to importation by a 4-year-old child visiting from Japan), health officials have observed that outbreaks may continue to occur when imported cases are introduced into settings such as schools with incomplete second-dose MMR coverage.