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Flu shot: Your best bet for avoiding influenza

Getting a flu shot often protects you from coming down with the flu. And while the flu shot doesn't always provide total protection, it's still worth getting.

By Mayo Clinic staff

The Food and Drug Administration (FDA) has approved the vaccines that will be available this fall to protect people against several seasonal flu (influenza) viruses expected to be in circulation this fall and winter.

This annual flu shot won't contain protection against the pandemic swine flu (novel H1N1) virus. A separate vaccine has been developed for the swine flu virus.

Influenza is a respiratory infection that sickens millions of people each year and can cause serious complications, especially in children and older adults. Fortunately, the flu vaccine — available in the form of a flu shot or a nasal spray — offers protection against the flu.

Here are the answers to common questions about flu shots.

When is the flu vaccine available?

The flu vaccine is generally offered between September and mid-November, which is typically before the late-fall to early winter start of flu season. However, getting a flu shot even later in the flu season may still protect you. It takes up to two weeks to build immunity following a flu shot.

Why do I need to get vaccinated every year?

You need annual flu protection because the influenza virus changes from year to year. The flu vaccine you got last year wasn't designed to fight the virus strains in circulation this flu season.

Influenza viruses mutate so quickly that they can render one season's vaccine ineffective by the next season. A Centers for Disease Control and Prevention (CDC) advisory committee meets early in the year to estimate which strains of influenza virus will be most prevalent during the upcoming flu season, and manufacturers produce vaccine based on those recommendations.

Who should get the flu vaccine?

Most people who want to reduce the risk of getting influenza can get a flu shot. The CDC recommends the flu vaccine each year if you:

  • Are age 6 months up to 19 years
  • Are pregnant
  • Are 50 years old or older
  • Have a chronic medical condition such as asthma, diabetes, or heart, kidney or lung disease
  • Have a weakened immune system such as from some medications or HIV infection
  • Are a resident of a nursing home or other long term care facility
  • Are a child care worker or health care worker or live with or care for someone at high risk of complications from the flu

Who shouldn't get the flu shot?

Don't get a flu shot if you:

  • Have had an allergic reaction to the vaccine in the past.
  • Are allergic to chicken eggs.
  • Developed Guillain-Barre syndrome, a serious autoimmune disease affecting the nerves outside the brain and spinal cord, within six weeks of receiving the vaccine in the past. People who have experienced Guillain-Barre after the flu vaccine are at higher risk than are others of developing it again.
  • Have a fever. Wait until your symptoms improve before getting vaccinated.

What are my options for the flu vaccine?

The flu vaccine comes in two forms:

  • A shot. A flu shot contains an inactivated vaccine made of killed virus. The injection is usually given in the arm. Because the viruses in the vaccine are killed (inactivated), the shot won't cause you to get the flu, but it will enable your body to develop the antibodies necessary to ward off influenza viruses. You may have a slight reaction to the shot, such as soreness at the injection site, mild muscle ache or fever. Reactions usually last one to two days and are more likely to occur in children who have never been exposed to flu virus.
  • A nasal spray. Administered through your nose, the nasal spray vaccine (FluMist) consists of a low dose of live, but weakened, flu viruses. The vaccine doesn't cause the flu, but it does prompt an immune response in your nose and upper airways as well as throughout your body.
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References
  1. FDA approves vaccine for 2009-2010 seasonal influenza. U.S. Food and Drug Administration. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm172772.htm. Accessed July 24, 2009.
  2. Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/protect/keyfacts.htm. Accessed July 24, 2009.
  3. Fiore AF, et al. Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR. 2009;58(early release):1. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr58e0724a1.htm. Accessed July 24, 2009.
  4. Inactivated influenza vaccine: What you need to know. Centers for Disease Control and Prevention. http://www.cdc.gov/vaccines/pubs/vis/downloads/vis-flu.pdf. Accessed July 24, 2009.
  5. Live, intranasal influenza vaccine: What you need to know. Centers for Disease Control and Prevention. http://www.cdc.gov/vaccines/pubs/vis/downloads/vis-flulive.pdf. Accessed July 24, 2009.

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Sept. 19, 2009

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