What are the possible side effects of the seasonal flu shot?

A seasonal flu shot, like any medicine could possibly cause serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small.

Serious problems from influenza vaccine are very rare. The viruses in inactivated influenza vaccine have been killed, so you cannot get influenza from the vaccine.

Mild problems:

• soreness, redness, or swelling where the shot was given
• hoarseness; sore, red or itchy eyes; cough
• fever
• aches If these problems occur, they usually begin soon after the shot and last 1-2 days.

Severe problems:

• Life-threatening allergic reactions from vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the shot.
• In 1976, a type of infl uenza (swine flu) vaccine was associated with Guillain-Barré Syndrome (GBS). Since then, flu vaccines have not been clearly linked to GBS. However, if there is a risk of GBS from current flu vaccines, it would be no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe influenza, which can be prevented by vaccination.

Last Reviewed: 10/28/2010

• What causes Guillain-Barre syndrome (GBS)?
• Do vaccines cause Guillain-Barre syndrome (GBS)?
• How common is Guillain-Barre syndrome (GBS), and how common is it after people are vaccinated for seasonal flu?

• Vaccines
  • Vaccine Safety