Antibody Response of an Elderly Population to a Supplemental Dose of Influenza B Vaccine

Recent reports have suggested that the antibody response of elderly persons to standard doses of influenza vaccine is depressed. We examined the effect of an additional threefold dose of influenza B vaccine on the antibody response in elderly, ambulatory veterans. One hundred thirty-one male subjects aged 70 years and older were randomized to receive one of three influenza vaccine regimens: Group I received standard trivalent influenza vaccine containing 15 micrograms of B/USSR/100/83 in one arm and placebo in the other; Group II received standard trivalent vaccine in one arm and a supplemental dose of 45 micrograms of B/USSR in the other; Group III received the same dose as group II combined in one arm with a placebo in the other. Antibody levels were measured at baseline, 1 month, and 5 months. Nearly 80% of the participants achieved levels of antibody to B/USSR considered protective; seroconversion rates varied from 40% to 61%. No significant differences in antibody response to B/USSR occurred among the vaccine groups, and there were more side effects at higher doses. The higher dose groups did, however, achieve greater antibody levels to the drifted influenza B virus which circulated during the year of the study. Response to the influenza A components of the vaccine, however, may have been blunted in Group III which received a large dose of A and B antigens all at one site.