during primary and secondary vaccination, and with varying routes of administration of the vaccines.

These studies should focus on immunogenicity and efficacy in populations at the extremes of age, especially infants and the elderly, including the very elderly. The interval required to induce a protective immune response after immunization is key to understanding the best vaccine for a pandemic setting. Responses that are reliably associated with reduced viral shedding must be defined and persistence of the immune response is another important factor.

Finally, it is important to generate experience with multiple pandemic vaccines to assess reactogenicity, immunogenicity, optimal dose, and route of administration. In our final analysis, gaining a broad understanding of the immune response to both natural infection and vaccines for as many different HA and NA viruses is a priority, as is looking not just at the standard serologic responses but also at cellular immune responses.