Factsheet about seasonal influenza
Influenza is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent flu is by getting a flu vaccine each year.
Systematic review of the efficacy, effectiveness and safety of newer and enhanced seasonal influenza vaccines
Overall the evidence base for the efficacy and effectiveness of newer and enhanced influenza vaccines appears limited at present, with a number of potentially relevant studies identified as ongoing.