Forty-three elderly individuals were immunized with Russian trivalent live cold-adapted influenza vaccine (LIV) and US trivalent influenza vaccine (IIV) administered separately or in combination. IL-2 production in vitro (in supernatants of cultures of lymphocytes stimulated with homologous viral antigens and PHA) and in vivo (in blood serum) and other factors of specific antiinfluenza immunity were compared. Vaccination of elderly subjects with commercial vaccines induced T-helper immunological memory, which manifests by increased secretion of IL-2 in vitro and in vivo. Simultaneous vaccination with LIV + IIV and revaccination (in 1 month) with LIV was the most effective method stimulating IL-2 production. The levels of IL-2 production in vitro were in good correlation with the secretion of this cytokin in vivo, lymph proliferation, and serum antibody production. No correlation between IL-2 production in vitro and the formation of local immune response (IgA in nasal swabs) was detected.