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How flu vaccines works

When a flu vaccine is given it stimulates your body's immune system to make antibodies to attack the flu viruses that are contained in the vaccine.

Antibodies are proteins that recognise and fight off germs, such as viruses, that have invaded your blood. It can take 10 to 14 days for immunity to build up fully after having a flu vaccine, so it is important to have a flu vaccine before flu starts to circulate.

No vaccine is 100% effective, but if you're exposed to a flu virus after you've had a flu vaccine, if the strain is one that was in the vaccine your immune system is likely to recognise the virus and produce antibodies to fight it.

If you are in a risk group you should have a flu vaccine every year, as the antibodies that protect you from flu decline over time, and the flu strains circulating in the community can also change from year to year.

How annual flu vaccines changes

Each year, the flu viruses that are most likely to circulate and cause health problems are identified in advance and vaccines are made to match them as closely as possible. The vaccines are recommended by the World Health Organization (WHO). Most flu vaccines contain 4 strains of the virus.

There are a number of different flu vaccines available again this season. With some working better than others in different age groups, they are broadly recommended by age and it is important to get a flu vaccine that is right for your age. Your doctor, nurse or pharmacist can advise on this.


Click here to see all vaccination leaflets.

Last Updated: 17/02/2022 16:04:13
The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website