Flu (also known as influenza) is a highly infectious illness caused by the flu virus. It spreads rapidly through small droplets coughed or sneezed into the air by an infected person. For most people, flu is unpleasant but not serious. You will usually recover within a week.
Studies have shown that flu vaccines provide effective protection against the flu, although protection may not be complete and may vary between people. Protection from the vaccine gradually decreases and flu strains change over time. Therefore, new vaccines are made each year and people at risk of flu are encouraged to be vaccinated every year.
The flu vaccination is offered to people in at-risk groups. These people are at greater risk of developing serious complications if they catch flu, such as pregnant women and elderly people.