A measles outbreak among adolescents

In a May, 1975, outbreak, 147 adolescents, ages 12 to 19 years, were identified as having measles by a physician or school nurse. One junior high school, with an enrollment of 1,122, contributed 131 of the cases. Of the 147 students, 54 were seen by physicians who also supplied their immunization records; 19 of 54 (35%) had received live measles virus vaccine without measles immune globulin, after age one year. The remaining 35 received: killed virus vaccine only (1), K + L (4), L + MIG (4), L at less than 1 year of age (4), L + ? MIG (4), immune serum globulin only, for exposure (6), no vaccine but history of measles previously (9); history uncertain (3). Hemagglutination-inhibition antibody titers were consistent with the diagnosis of acute measles in 11 children. No index case was identified and no secondary cases occured within the families of the 54 cases. This measles outbreak among seemingly immunized adolescents raises a serious question as to the duration of such protection.