Influenza virus epidemics are responsible for approximately 1 million human deaths annually, and a pandemic caused by H5N1 avian influenza viruses could result in over 50 million deaths. Current vaccine strategies cannot prevent the first wave of an influenza pandemic because their formulation is virus-strain specific and requires advance knowledge of the specific virus strain circulating in any given year. We must develop innovative vaccine strategies in order to vaccinate effectively against newly emerging and highly virulent influenza virus strains. Since CD4 T-cell responses are required for long-lived and protective B-cell and CD8 T-cell immunity, new vaccines must be designed to elicit both T- and B-cell immunity against a broader range of influenza virus strains.