Universal influenza vaccines, science fiction or soon reality?

Currently used influenza vaccines are only effective when the vaccine strains match the epidemic strains antigenically. To this end, seasonal influenza vaccines must be updated almost annually. Furthermore, seasonal influenza vaccines fail to afford protection against antigenically distinct pandemic influenza viruses. Because of an ever-present threat of the next influenza pandemic and the continuous emergence of drift variants of seasonal influenza A viruses, there is a need for an universal influenza vaccine that induces protective immunity against all influenza A viruses. Here, we summarize some of the efforts that are ongoing to develop universal influenza vaccines.