How the flu shot works
Flu shots assist your body's natural ability to defend itself. Every year, physicians and scientists work to make the best flu vaccine possible. Typically, they start by finding three or four of the most common flu viruses for that particular season. Then, they expose the viruses to heat until they fall apart. The flu vaccine teaches your body's immune system how to recognize those three or four types of flu. If and when your immune system encounters that year's flu virus, it will know just what to do.