I got the flu shot last year, but I still got the stomach flu. Why should I bother getting it again this year if it doesn't work?

Answers from James M. Steckelberg, M.D.

The flu shot protects against influenza, which isn't the same thing as the stomach flu (gastroenteritis). Gastroenteritis is an infection caused by a variety of viruses, including rotaviruses and noroviruses. Although it is often called the stomach flu, gastroenteritis is not caused by influenza viruses.

Influenza attacks your respiratory system — your nose, throat and lungs. Signs and symptoms of influenza may include:

  • Coughing
  • Congestion
  • Fever
  • Muscle aches

Gastroenteritis, on the other hand, attacks your intestines, causing signs and symptoms such as:

  • Diarrhea
  • Vomiting
  • Fever
  • Chills
  • Headache
  • Body aches

You can reduce your risk of influenza and gastroenteritis by washing your hands often with soap and water, as well as disinfecting contaminated and frequently touched surfaces.

The annual flu vaccine is the most effective way to reduce your risk of getting influenza. Two oral rotavirus vaccines are available for young infants — RotaTeq and Rotarix.

Feb. 03, 2015 See more Expert Answers