The goals of the workshop were to identify gaps in our knowledge and abilities to address the unique challenges encountered in the development of vaccines intended to protect against pandemic influenza and to facilitate implementation of a global research agenda to improve efficacy assessment of pandemic influenza vaccines. This workshop included discussions on: (i) current knowledge regarding immune correlates of protection against seasonal influenza; (ii) human immune responses to avian influenza infection and vaccines for novel influenza viruses; (iii) limitations of currently available assays to evaluate vaccine immunogenicity; and (iv) potential insights from animal models for correlates of protection against avian influenza.