Serious Side Effects of the Flu Shot

Each fall, seasonal flu shots become widely available to the general population. Many health care professionals encourage vaccines to minimize potentially dangerous outbreaks of flu. What are the side effects of these vaccines? Do the benefits outweigh the risk?

Serious Side Effects of the Flu Shot
Serious Side Effects of the Flu Shot (Image: LittleBee80/iStock/Getty Images)

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The flu--or influenza--is a virus causing respiratory infection, high fever, body aches and general illness. Unlike other respiratory illnesses, influenza symptoms are usually more severe. With 200,000 hospitalizations and approximately 36,000 deaths annually, seasonal influenza can pose a grave health issue. Those contracting influenza may develop a "super infection" which is a bacterial infection in addition to the flu symptoms.

Flu (Image: Jupiterimages/Pixland/Getty Images)


Seasonal vaccines contain three types of influenza viruses researchers predict will be effective against the upcoming flu events. These vaccines may be given in a needle or in a nasal spray form. The injection dosage contains killed viruses. In the nasal spray form (FluMist), the virus is alive, but considerably weakened so it will prevent flu, without maturing in the body.

FluMist (Image: Christopher Polk/Getty Images Entertainment/Getty Images)


According to the Centers for Disease Control, the effects of the seasonal influenza vaccine are usually mild. In adults, fewer than 20 percent experience side effects of soreness, redness or slight swelling at the injection site. Other symptoms following the flu shot, (low grade fever, chills and muscle aches) appear in less than 1 percent of adults. Adults receiving the live nasal spray dosage may exhibit congestion, runny nose, head or sore throat. Children may display the same symptoms, along with slight wheezing or possible vomiting. Again, these conditions are typically mild, temporary, and not reported by all receiving vaccines.

Flu shot
Flu shot (Image: Spencer Platt/Getty Images News/Getty Images)


Developing mild flu-like symptoms does imply the flu shot causes influenza. These side effects are brief and are due to the body's immune response. Some concern was raised about the potential link between flu shots containing the preservative Thimerosal and autism in recent years. After numerous studies, no correlation has ever been documented. However, as a safeguard, vaccine manufacturers have removed or reduced Thimerosal to trace amounts.

Flu shots
Flu shots (Image: Justin Sullivan/Getty Images News/Getty Images)


The most serious side effects of the flu shots are extremely rare and have been related to either allergic reactions or a neurological condition, called Guillain-Barre Syndrome (GBS). Flu shot vaccine is incubated in chicken eggs. Egg proteins left in the vaccine may prompt allergic responses. Consult your physician if you have a serious allergy to eggs before receiving influenza shots. Packaging of flu is often in syringes or vials containing rubber or latex. Those with a serious allergy to latex, (as with egg allergies), should consult a physician.

Eggs (Image: ddsign_stock/iStock/Getty Images)


GBS, which causes temporary to permanent neurological damage, has been associated with only one type of influenza vaccine. The CDC cites studies suggesting chances of acquiring GBS from current vaccines is less than one in a million.

Flu shot
Flu shot (Image: John Moore/Getty Images News/Getty Images)


Though some mild flu-like symptoms may appear, chances of serious side effects of seasonal flu shots are very nominal. Those who obtain a flu shot minimize the greatest risk, which is contracting influenza.

Flu shot
Flu shot (Image: Spencer Platt/Getty Images News/Getty Images)


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