A flu shot is a vaccine designed to protect against the influenza virus, which causes the flu. It works by stimulating the immune system to produce antibodies that can fight off the virus. The flu shot is typically recommended annually, as the virus can change from year to year, and the vaccine is updated to match the most common strains. Getting a flu shot can help reduce the risk of severe illness, hospitalization, and complications related to the flu. It is especially important for vulnerable populations, such as the elderly, young children, and individuals with certain health conditions, to receive the vaccine to maintain their health during flu season.