I get the flu shot every year and never get the flu. If you think you have the flu, then check the internet for the actual symptoms of influenza. They are considerably different from what most people usually think of as "the flu". Many people can get very sick from a cold, can develop a very bad cough, fever, headache and achy feeling and still not have the flu. It takes a lab test of your blood to determine if you actually have the flu. The flu is dangerous and kills many people each year which is why they have the shots.It seldom lasts less than two horrible weeks and frequently is longer. People are usually bedridden because they are too sick to be out of bed.
The flu is so dangerous that the government keeps records on how many people actually have contracted it each year, how many have died each year. Very few people every have a mild case of the flu.