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All About the Seasonal Flu Shot

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Updated October 29, 2009

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

What Is the Seasonal Flu Shot:

Every year, scientists work to predict which flu viruses will be circulating during the next flu season. These viruses are then used to make a vaccine, a medication that is given as a shot and helps to prevent you from getting the flu. The shot is usually given in the arm in adults and in the thigh in small children.

Because the virus in the vaccine is a guess at which viruses will be present in a given flu season, you may still get the flu even if you've had the shot. However, the immunity you have developed as a result of the flu shot can decrease the severity of the illness.

Who Can Get the Seasonal Flu Shot:

In general, most healthy people who want to reduce their chances of getting the flu can get the seasonal flu shot. However, certain individuals are highly encouraged to get the seasonal flu shot because they are more at risk of having complications from the seasonal flu. These individuals include: children aged 6 months to 19 years of age (especially small children in daycare), pregnant women, people older than age 50, people with chronic medical conditions, people who live in care facilities such as nursing homes, health care workers, and people who live with others at high risk of developing flu complications.

Who Should Not Get the Seasonal Flu Shot:

Infants less than 6 months old, individuals with allergies to eggs, and anyone who has had a previous severe reaction to the flu shot (particularly anyone who has developed Guillain-Barré syndrome after getting a flu shot) should not get the seasonal flu shot. In addition, anyone who currently has a flu-like illness should wait until they have recovered before getting the seasonal flu shot.

What Are Side Effects of the Seasonal Flu Shot:

The virus in the seasonal flu shot is not live - meaning you cannot actually get the flu from the seasonal flu shot. (The virus in the FluMist is live, but should not be confused with the virus in the seasonal flu shot.)

Even though you cannot get the flu from the seasonal flu shot, the following side effects have been reported: redness, soreness, a small amount of swelling at the injection site, a low-grade fever, aching in the arm or leg where the shot was given, and, sometimes, widespread body aches. These side effects usually don't last more than a day or two.

When Should I Call A Doctor:

Severe reactions to the seasonal flu vaccine are rare. You should call the doctor or go to the emergency room if you have: a high fever, difficulty breathing, hives, weakness, a fast heart beat or dizziness.

According to the CDC, Guillain-Barré syndrome occurred as a side effect of a swine flu (H1N1) vaccine that was created in 1976, but has not been associated with flu shots since.

Is the Seasonal Flu Shot Linked to Autism:

There has been a lot of controversy concerning vaccinations and autism. Individuals who think autism is linked to vaccinations believe it is related to a mercury-based preservative in vaccines called thimerosal.

The government has removed thimerosal from almost all vaccines, but it is still present in some seasonal flu vaccines. Currently, it is present in multi-dose vials of the flu vaccine. Single-dose vials, however, are preservative-free.

If you are worried about autism from vaccinations, visit http://www.cdc.gov/flu/about/qa/thimerosal.htm and talk to your physician before getting the seasonal flu shot.

Special Note For the 2009-2010 Flu Season:

In April 2009 a flu virus emerged and was eventually identified as swine flu or H1N1. Because the virus emerged so late in the season it was not included in the seasonal flu shot for 2009-2010. A separate vaccination has been manufactured to protect against H1N1. You can find more information about this special vaccination here: CDC 2009 H1N1 Influenza Vaccine

Sources:

CDC. Key Facts About Seasonal Flu Vaccine. Accessed: October 22, 2009 from http://www.cdc.gov/FLU/protect/keyfacts.htm

CDC. Thimerosal in Seasonal Influenza Vaccine. Accessed: October 22, 2009 from http://www.cdc.gov/flu/about/qa/thimerosal.htm

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