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Flu Shot: The Vaccine and Its Side Effects

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    The shots and the nasal spray prompt your body to get ready to fight an infection with the flu virus. These tools, called antibodies, fight the virus when you’re exposed to it.

    Each year, the flu vaccine has a few different types of the virus. Scientists choose the strains based on the ones they think are most likely to show up that year.

    The vaccine itself cannot cause the flu. Sometimes, people who get vaccinated during flu season catch the virus in the 2 weeks before the vaccine has a chance to fully work. It's human nature to see a link between the two events, but there's no evidence that the vaccines cause flu or make people more likely to get it. And even though these vaccines are not 100% effective -- people sometimes get sick even though they had a flu shot -- vaccinated people almost always have a milder illness than people who weren't vaccinated.

    Who should get the shot?

    Everyone ages 6 months and older should get one every year. It's very important for people who are more prone to flu complications, such as pneumonia. Those at higher risk include:

    • Children younger than age 5, but especially those younger than 2
    • People age 65 and older
    • Women who will be pregnant during flu season
    • People who live in nursing homes
    • Anyone with long-lasting heart or lung conditions, including asthma, or with any health problem that weakens the immune system, such as diabetes or HIV
    • Caregivers, including baby sitters, of any children younger than 5. It’s especially important for people who care for infants younger than 6 months. (These children are too young to get the flu vaccine.)
    • Any person in close contact with someone in a high-risk group, such as people in their households or health care workers

    Should I talk to my doctor before I get a flu shot?

    Some people should make sure it’s OK to get vaccinated. Ask your doctor first if:

    • You’ve had an allergic reaction to a flu shot in the past.
    • You’ve had Guillain-Barre syndrome that happened after you got the flu vaccine. That’s a disorder in which the body's immune system attacks part of the nervous system.
    • You’re very ill. If you have a mild illness, it's OK to get vaccinated. Otherwise, talk to your health care provider.

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