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Flu Shot: The Vaccine and Its Side Effects

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    The flu vaccine is the best way to protect yourself from the influenza virus. It may sound like a minor illness, butit can cause dangerous problems for some people. It can even be deadly.

    Learn the facts about the vaccine so you’ll be ready to stay flu-free.

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    When should I get vaccinated?

    Peak flu season may begin as early as October and run through May. The best time to get a flu shot is as soon as it’s available, usually in September or October. It takes about 2 weeks for the shot to be most effective. You can still get the vaccine in December or later, but the earlier in flu season you get it, the better your odds of staying well.

    What types of the vaccine can I get?

    There are several:

    • The traditional flu shot is an injection into your muscle. It’s made from pieces of flu viruses.
    • Egg-free flu shot. Unlike other flu vaccines, this one is not grown inside eggs. It’s an option for people who have egg allergies.
    • The high-dose flu shot is for people age 65 and older, who may need a stronger dose to get the same protection.
    • An intradermal flu shot uses a tiny needle that only goes skin deep. It’s for people ages 18 to 64.
    • Nasal spray flu vaccine (FluMist). No needle necessary with this. It’s made from weakened, live flu viruses. Another name for it is LAIV (live attenuated influenza vaccine). It’s for healthy people ages 2 to 49 who aren’t pregnant and who don’t have weak immune systems. Check with your doctor to make sure it’s the right choice for you.

    There are vaccines that protect against three influenza virus strains (called trivalent vaccines) or four strains (called quadrivalent vaccines). The traditional flu shot comes in both forms. The high-dose and intradermal shots come only in the trivalent form. And the nasal spray flu vaccine is available only in the quadrivalent form.

    How does the vaccine prevent flu?

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