The influenza vaccine is a medical preparation designed to protect against the influenza virus, which causes the flu. It works by stimulating the immune system to recognize and fight the virus, reducing the risk of illness. The vaccine is typically updated each year to match circulating strains of the virus. There are different types of influenza vaccines, including inactivated vaccines, live attenuated vaccines, and recombinant vaccines. They are usually administered through an injection or nasal spray. Getting vaccinated is recommended for most people, especially those at higher risk, such as the elderly, young children, and individuals with certain health conditions.