The immunoglobulin response to reimmunization with rubella vaccine.

An adolescent military dependent population, 86% of whom had documented history of rubella immunization, was screened by two commercially available rubella hemagglutination inhibition tests. All those who were R-HAI antibody negative were immunized, and postvaccination sera were examined for the development of rubella-specific antibody (R-IgM). R-IgM was not found in any of the previously immunized subjects despite the lack of R-HAI antibody. R-IgM was detected in two seronegative subjects who had no documentation of previous rubella immunization. Thus, although the R-HAI antibody had waned, the engrams of previous immunization remained, resulting in a secondary response on re-exposure. The development of a secondary immune response, despite the absence of detectable r-HAI antibody, casts doubt on the validity of R-HAI as a screening test to determine rubella immunity. The data support continuing mass immunization of preschool children and vaccination of all older females who lack documentation of rubella immunization.