Getting the influenza vaccine is the most effective way to reduce the chance of becoming infected with the flu. People who get the influenza vaccine have a lower chance of illness and death from influenza compared with people who are not vaccinated. (See "Seasonal influenza vaccination in adults" and "Seasonal influenza in children: Prevention with vaccines".)

Initially, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a nuisance, you usually feel much worse with the flu. Common signs and symptoms of the flu include: Fever over 100 F (38 C) Aching muscles, especially in your back, arms and legs Chills and sweats Headache Dry, persistent cough Fatigue and weakness Nasal congestion Sore throat