Measles (rubeola) susceptibility among elementary schoolchildren.

Measles (rubeola) immunity among 479 elementary schoolchildren from suburban Minneapolis was serologically surveyed in December 1971. Of the 479 children, 25 (5.2%) had hemagglutination-inhibition (HI) titers less than 2. These children were considered susceptible to measles. For the 233 immunized children with no measles history, 13 (5.6%) had rubeola HI titers less than 2 while 5 (5.1%) of the 98 youngsters with a history of clinical measles had rubeola HI titers less than 2. Of the 454 immune children, 73 (16%) had measles HI titers between 2 and 8. These findings confirm durable immunity and a low rate of vaccine failure following live attenuated measles vaccination but demonstrate the importance of testing sera beginning at a dilution of 2 in order to detect children with low antibody levels. This survey also suggests that maternal antibody interferes with the active immune response in youngsters immunized when less than 1 year of age because this group of children had significantly lower geometric mean titers and significantly more susceptibles than the children immunized when greater than or minus 2 years.