Responses of elderly and chronically ill subjects to bivalent influenza A/New Jersey/8/76 (Hsw1N1)-A/Victoria/3/75 (H3N2) vaccines.

Antibody responses and side effects to bivalent influenza A virus vaccines from three different manufacturers, containing 200 or 400 chick cell-agglutinating (CCA) units each of A/New Jersey/8/76 (Hsw1N1) and A/Victoria/3/75 (H3N2) antigens, were evaluated in 234 ambulatory elderly and chronically ill volunteers in a placebo-controlled, doubld-blind study. Systemic reactions did not occur significantly more often among recipients of vaccine than among volunteers who received placebo. Local reactions to vaccines were observed but were mild, transient, and well tolerated. Occurrence of preexisting antibody to each antigen was common. Titers of antibody to A/New Jersey/8/76 (Hsw1N1) antigen of greater than or equal to 1:40 occurred after immunization in 94%-100% of volunteers receiving vaccines and in 66% of the placebo recipients. Titers of antibody to A/Victoria/3/75 (H3N2) antigen of greater than or equal to 1:40 occurred in 53%-85% of vaccine recipients compared with 34% of those in the placebo group. Thus, bivalent split-product and whole-virus influenza I vaccines containing 200/200 or 400/400 CCA units of the two antigens appeared to be nearly equivalent in incidence and severity of side effects and antibody responses in recipients.