Immunity to measles in a large population of varying age. Significance with respect to vaccination.

During a measles outbreak, 660 hospital employees of widely varying ages were screened for immunity to the disease using an automated indirect fluorescent antibody technique. Of these 660 employees, 623 indicated their year of birth; 21 were seronegative and 13 had borderline titers. Of those born before 1957, 7 tested seronegative and 6 were borderline, while 12 of those born between 1959 and 1964 were seronegative and 3 were borderline. There are several possible reasons for these findings. It is concluded that mass immunization of high-risk populations during outbreaks, while effective, is difficult to justify scientifically because only a small percentage of subjects are not immune. If facilities permit, mass screening during outbreaks may be feasible. Preferably, continuous screening and vaccination of susceptible high-risk employees could be performed. Our study also does not validate exclusion from immunization programs those born prior to 1957 in view of the fact that both seronegativity and disease occur in this age group with significant frequency.