Influenza is a virus that causes a respiratory illness and is considered to be highly contagious. Each year, the flu is responsible for thousands of hospitalizations and hundreds of deaths.
The flu shot often contains three to four strains. While many strains of the flu exist in the world, the three to four strains in the flu shot are predicted to be the most common ones that will hit during the flu season. CDC Officials Recommended Flu Shots
Because the flu shot does not protect you from all the strains, you are not guaranteed to be flu-free. However, your chances of getting the flu are drastically cut when you get a flu shot.
A common myth about the flu shot is that you get protection soon after getting receiving the vaccine, which is not true. In order for you to become fully protected from the flu, your body has to develop an immune response to the vaccine. In other words, it takes time for your body's immune system to kick in and protect itself. On average, it takes about two weeks for you to become protected by the flu shot. During these two weeks, avoid close contact with people who are sick.
If you are interested in getting a flu shot, talk to your doctor or pharmacist.