Risk for measles related to immunization status in two Tucson high schools

An outbreak of measles occurred in Tucson, AZ, in 1985; 112 of the 225 cases were among students at two large high schools. A review of the immunization records of all students at both schools was undertaken in order to assess the risk of a person contracting measles in relation to that person's immunization status. Two factors, the lack of an immunization record and immunization prior to 12 months of age, showed a positive association with contracting measles. The association was statistically significant at one high school but not the other. At the first high school, students who were immunized at 12 to 14 months of age had a greater risk of infection than those immunized at 15 months or older. However, age at immunization of 12 to 14 months was not associated with a significantly higher risk when persons with multiple doses of vaccine were excluded from the analysis. Students of both schools showed a lower attack rate for those who had received multiple doses of vaccine, but the difference was not statistically significant.