Epidemic rubella in military recruits.

Between Dec 1 and Feb 18, 1976, 320 cases of rubella occurred among recruits and dependent children at two Air Force bases in Illinois and Texas. Only 28 cases (9%) were identified in patients aged 17 and under. Routine serosurveilance before the outbreak revealed protective immunity in 89.1% of trainees. This outbreak emphasizes the changing epidemiology of what was formerly considered a childhood illness, and underscores the failure of herd immunity.