Efficacy of a vaccine that links viral epitopes to flagellin in protecting aged mice from influenza viral infection

► We show that a vaccine linking flagellin with hemagglutinin protects aged mice from influenza viral lung infection. ► Our results demonstrate that a high dose of vaccine was effective in aged mice, although the induced protection was inferior to that found in young mice. ► Defects in adaptive immune system were associated with the reduced efficacy of the vaccine in aged mice.