Abstract
Influenza virus infections yearly cause high morbidity and mortality burdens in humans, and the development of a new influenza pandemic continues to threaten mankind as a Damoclean sword. Influenza vaccines have been produced by using egg-based virus growth and passaging techniques that were developed more than 60 years ago, following the identification of influenza A virus as an etiological agent of seasonal influenza. These vaccines aimed mainly at eliciting neutralizing antibodies targeting antigenically variable regions of the hemagglutinin (HA) protein, which requires regular updates to match circulating seasonal influenza A and B virus strains. Given the relatively limited protection induced by current seasonal influenza vaccines, a more universal influenza vaccine that would protect against more-if not all-influenza viruses is among the largest unmet medical needs of the 21st century. New insights into correlates of protection from influenza and into broad B- and T-cell protective anti-influenza immune responses offer promising avenues for innovative vaccine development as well as manufacturing strategies or platforms, leading to the development of a new generation of vaccines. These aim at the rapid and massive production of influenza vaccines that provide broad protective and long-lasting immunity. Recent advances in influenza vaccine research demonstrate the feasibility of a wide range of approaches and call for the initiation of preclinical proof-of-principle studies followed by clinical trials in humans.