Seasonal 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.
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 jab 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.
This year's flu jab (2011/12)
This winter’s flu jab protects against the same three strains of flu as last year’s vaccines. These include the H1N1 strain of the flu virus. H1N1 is the same strain of flu that caused the 2009 swine flu pandemic.
H1N1 is included because it is likely to be one of the major flu strains circulating in Britain this winter.
The best time to have a flu jab is in the autumn, from September to early November.