What are the risks from an influenza vaccine?
A vaccine, 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 inactivated flu vaccine are very rare. The viruses in inactivated influenza vaccine have been killed, so you cannot get influenza from the vaccine.
Mild problems include soreness, redness, or swelling where the shot was given fever aches If these problems occur, they usually begin soon after the shot and last 1-2 days.
Severe problems, such as life-threatening allergic reactions from vaccines, are very rare. If they do occur, it is within a few minutes to a few hours after the shot. In 1976, swine flu vaccine was associated with a severe paralytic illness called Guillain-Barré Syndrome (GBS). Influenza vaccines since then have not been clearly linked to GBS. However, if there is a risk of GBS from current influenza vaccines, it is estimated at 1 or 2 cases per million persons vaccinated - much less than the risk of severe influenza, which can be prevented by vaccination.
