The human influenza virus is the causative agent of one of the most important infectious diseases in the world, causing frequent (seasonal) epidemics as well as pandemics, both of which cause significant morbidity and mortality worldwide. Influenza virus infects all age groups but children and adults over the age of 65 are most at risk of severe morbidity and mortality. Vaccination is recommended for these age groups. Vaccination remains the most effective method to control seasonal infections and the most important strategy to prepare for a possible pandemic. Despite the development and licensure of influenza vaccines along with clinical evidence of their ability to protect against influenza, the potential correlates of protection induced by these vaccines are still not fully elucidated

The availability of a tool-box of standardised, validated serological assays for human influenza vaccines, agreed and used by key parties in the private and in the public sector will have tremendous impact on the R&D process globally, and will pave the way for future investigation and definition of correlates of protection for these vaccines.