H1N1 flu (swine flu) vaccine Q & A

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H1N1 flu (swine flu) vaccine Q & A

Photo of James Steckelberg, M.D.
James Steckelberg, M.D.

The 2009 H1N1 flu (swine flu) pandemic is over, but the virus is still out there, making the rounds as a "regular" strain of seasonal influenza A. With a new flu season on the way, here's an update on the flu vaccine.

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. It takes up to two weeks to build immunity after a flu shot.

Will I still have to get a separate vaccine for swine flu?

No. The flu vaccine is formulated each year to protect against the three influenza viruses expected to be the most common during that year's flu season. The seasonal flu shot for 2010-11 protects against the 2009 pandemic H1N1 flu, as well as against another strain of influenza A (H3N2) and an influenza B virus.

Who should get the flu vaccine?

In the United States, the flu vaccine is recommended for everyone beginning at 6 months of age. According to the Centers for Disease Control and Prevention, the flu vaccine is particularly important for older people, pregnant women and young children — the groups with the highest rates of flu complications.

Why does everyone need vaccination every year?

Influenza viruses mutate so quickly that they can render one season's vaccine ineffective by the next season. Health officials use information gathered from around the world to determine which strains of influenza virus are most likely to be prevalent during the upcoming flu season. Manufacturers produce vaccine based on those recommendations.

The vaccine's effectiveness is usually strongest during the first six months after receiving a flu shot. After that, the strength of the protection it provides begins to diminish.

How is the flu vaccine administered?

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.
  • 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.

Because a standard flu shot may not trigger as strong an antibody response in older people as it does in young adults, a higher-dose vaccine has been approved for use in people age 65 and older.

Why do children need two doses of the flu vaccine?

Children younger than 9 years old require two doses of the flu vaccine, spaced at least four weeks apart, if it's the first time they've been vaccinated for influenza. That's because children don't develop an adequate antibody level the first time they get the vaccine. If a flu vaccine shortage occurred and your child couldn't get two doses of vaccine, one dose might still offer some protection.

Who should not get flu vaccine?

Don't get a flu shot if you:

  • Have had a bad reaction to the vaccine in the past
  • Are allergic to chicken eggs
  • Have a fever
Last Updated: 2010-09-18
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