When you get a flu shot you are injected in the arm with the influenza vaccine. The influenza virus is always present somewhere in the world. In the United States flu outbreaks tend to occur each year between November and March.
Influenza causes a coldlike upper respiratory infection.
Unlike most colds, however, the flu often causes fever, muscle aches, and dizziness. It can also lead to more serious infections, such as pneumonia. These deaths usually occur in the elderly and in people with chronic health problems, such as heart disease and severe asthma. They predict which strains of flu virus are most likely to appear the next winter. This means you cannot catch the flu from getting a shot.