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Flu Shot Reactions

With the new flu season, it’s time for another round of flu shots. Each year, a new flu shot is developed specifically to fight the strain of flu virus expected for the coming season. Because the influenza virus mutates each year, the shot you got last year won’t cover you. That’s not good news for those who have suffered an adverse flu shot reaction.

Some adverse flu shot reactions are common, even expected, and others are rare. Depending on the reaction and the severity, you and your doctor may decide that the flu shot is not worth the risk.

Common Reactions

Most people who get a flu shot have little reaction from it. Common side effects that may occur are:

Redness, soreness, or swelling at the injection site Low grade fever Muscle aches
The soreness at the injection site may be from the needle stick. Once the vaccine is introduced, the body’s immune system begins to make protective antibodies that will later be used to fight the flu virus. The production of these antibodies may cause the swelling and aches. These symptoms don’t occur very often and when they do, they last 1-2 days. Symptoms may be treated with acetominophen or ibuprofen, available over-the-counter.

Allergic Reactions

Anyone who has had a previous allergic reaction to flu vaccine or is allergic to eggs should discuss with their doctor before getting a flu shot.

The flu vaccine is made in a process that uses eggs. Minute amounts of egg protein remain in the flu shot. People with egg allergy may still take the flu shot, but expect to remain in the office for a time to watch for any signs of allergic reaction.

Anyone can develop a sudden allergic reaction, even if they have taken flu shots before without a problem. Allergic reactions to flu shots are very rare. They usually occur within a few minutes, but may not show up for several hours.

Signs of allergic reaction are:

Breathing problems Hoarseness or wheezing Hives Pale skin Weakness Rapid heart rate Dizziness
If any of these symptoms occur, notify your doctor right away. Any sign of breathing problems is a medical emergency; seek help immediately.

Rare Reactions

Guillain-Barre’ syndrome is characterized by fever, muscle weakness, and nerve damage, which may lead to complete paralysis. Though the syndrome is usually reversible, recovery may take months. In 1976, there was a suspected association between Guillain-Barre’ syndrome and swine flu vaccines. The disease normally occurs in one per 100,000 people each year. Research studies have been done to look for a relationship between flu shots and Guillain-Barre’ syndrome, but only one study found a link. That study estimated that one person for every one million people vaccinated is at risk for the disease.

Will the Flu Shot Give Me the Flu?

The flu shot is made with inactive (killed) virus. You cannot get the flu from the flu shot. The soreness and muscle aches that occur in some people may be mistaken for flu symptoms. If exposed to the flu just prior to getting the shot, a person may still develop the flu. Those who take the nasal vaccine may complain of a sore throat and runny nose, but this is a side effect of the vaccine and not the flu.

I Had a Reaction. What Should I Do?

If you experience an adverse flu shot reaction, contact your doctor or health care provider. For signs of an allergic reaction, especially breathing problems, get emergency medical attention.

You may want to ask your doctor or nurse to report the reaction to the Food and Drug Administration (FDA). They track all adverse reactions using theusing the Vaccine Adverse Event Reporting System (VAERS) form. The form may also be filed online by any patient, parent, or caregiver at http://vaers.hhs.gov/index or by calling VAERS at 1-800-822-7967.


Center for Disease Control Flu website: http://www.cdc.gov/flu