Changing epidemiology of mumps and its impact on university campuses.

The reported incidence of mumps has declined dramatically since licensure of the live attenuated mumps vaccine in the United States in 1967, particularly in young children. Because administration of the vaccine was not widely practiced during the first decade it was available, there is now a cohort of teenagers and young adults who are relatively underimmunized. Reported mumps cases in this cohort increased substantially during 1986 to 1987. Mumps outbreaks at three Illinois universities, from which 123 clinical cases were reported between September 1986 and May 1987, were investigated. Meningeal involvement was reported in 17% of case-patients, orchitis occurred in 19% of 64 men, 6% of patients were hospitalized, and direct health care costs were estimated at $264 per case and more than $32,000 for the three outbreaks combined. The risk of mumps illness was greater for students less than 20 years of age (relative risk [RR] = 2.1, 95% confidence interval [CI] = 1.4, 3.1); students residing in dormitories (RR = 2.7, 95% CI = 1.6, 4.6); and out-of-state students (RR = 1.8, 95% CI = 1.0, 3.0). Because the available data suggest that mumps in college-aged persons is due chiefly to a failure to vaccinate susceptible persons, colleges and universities should become one major focus of mumps prevention activities to reduce susceptibility in this high-risk population.