The study of safety and immunizing properties of a live influenza vaccine from influenza viruses type A (H1N1) and A (H3N2) used separately and in combination was carried out in 2461 children ranging in age from 3 to 15 years. The possibility of combining two influenza type A viruses with similar biological activity was demonstrated. The vaccine exerted no harmful effect in children and actively stimulated the production of antihemagglutinating, antineuraminidase, and secretory antibodies and enhanced the formation of cell-mediated immunity.