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.

Flu transmits easily from person to person. It does this through the air or from contaminated hands or surfaces. The risk of getting or causing infection is easily reduced by taking some simple preventive steps. Immunisation in particular decreases the risk of a person being infected. Proper use of flu vaccines is the most effective form of protection.

Injected trivalent inactivated influenza vaccines are most commonly used throughout the world. Influenza antigen preparation varies between manufacturers. The inactivated influenza vaccines available in the EU/EEA may contain either split virion influenza virus products or subunit influenza products.