Serological response to rubella revaccination.

To document the serological response, 21 seronegative rubella vaccinees (hemagglutination inhibition [HI] titer less than 10) were revaccinated with RA 27/3 rubella vaccine. All demonstrated an anamnestic response. Although RA 27/3 vaccine was an effective booster, antibody boost was not maintained in some persons. Of 15 persons tested, 24 to 27 months after revaccination, six had a significant HI antibody drop (fourfold or greater); only one had lost all detectable HI antibody. Although all 21 study participants were initially HI seronegative by rubella HI testing, 16 (76.2%) possessed neutralization and/or enzyme-linked immunosorbent assay antibodies before revaccination. As more persons with vaccine-induced immunity join the adult population pool, more sensitive test methods may be needed to assess serological status accurately.