Flu shot: Your best bet for avoiding influenza

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Flu shot: Your best bet for avoiding influenza

This year's annual flu shot will offer protection against the pandemic H1N1 flu (swine flu) virus, in addition to two other influenza viruses that are expected to be in circulation this fall and winter.

Influenza is a respiratory infection that can cause serious complications, particularly to young children and older adults. Flu shots are the most effective way to prevent influenza and its complications. The Centers for Disease Control and Prevention (CDC) now recommends that everyone 6 months of age or older be vaccinated annually against influenza.

Here are the answers to common questions about flu shots.

When is the flu vaccine available?

The seasonal flu vaccine generally becomes available in late summer or early fall, before the start of flu season. Shipment of the 2011-12 vaccine started in August 2011 and was expected to continue through September and October. It takes up to two weeks to build immunity after a flu shot. But you can benefit from the vaccine even if you don't get it until flu season starts.

Why do I need to get vaccinated every year?

New flu vaccines are released every year to keep up with rapidly adapting flu viruses. Because flu viruses evolve so quickly, last year's vaccine may not protect you from this year's viruses.

After vaccination, your immune system produces antibodies that will protect you from the vaccine viruses. In general, though, antibody levels start to decline about six months after you receive the vaccine — another reason to get a flu shot every year.

Who should get the flu vaccine?

Since the 2010-11 influenza season, the CDC has recommended annual influenza vaccinations for everyone age 6 months or older. Vaccination is especially important for people at high risk of influenza complications, including:

  • Pregnant women
  • Older adults
  • Young children

Chronic medical conditions can also increase your risk of influenza complications. Examples include:

  • Asthma
  • Cerebral palsy
  • Chronic obstructive pulmonary disease (COPD)
  • Cystic fibrosis
  • Epilepsy
  • HIV-AIDS
  • Kidney or liver disease
  • Muscular dystrophy
  • Obesity
  • Sickle cell disease

Who shouldn't get the flu shot?

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 that day

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.
  • A nasal spray. 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.

What are the main differences between the two types of flu vaccine?

Both the flu shot and the nasal spray help protect you from influenza. But there are differences to consider before deciding between the two.

Flu shotNasal spray
Administered through a needle — you'll need an injection Administered through a spray — you won't need an injection
Contains killed viruses — you can't pass the flu along to anyone else Contains weakened live viruses that won't give you the flu but that can, in rare cases, be transmitted to others
Approved for use in people 6 months of age and older Approved for healthy people ages 2 to 49 years
Can be used in people at increased risk of flu-related complications, including pregnant women and those with chronic medical conditions Given only to nonpregnant healthy people, not to those with chronic medical conditions, suppressed immune systems, or to children and adolescents receiving aspirin therapy

Can the vaccine give me the flu?

No. The flu vaccine can't give you the flu. But you might develop flu-like symptoms — despite getting a flu shot — for a variety of reasons, including:

  • Reaction to the vaccine. Some people experience muscle aches and fever for a day or two after receiving a flu shot. This may be a side effect of your body's production of protective antibodies. The nasal vaccine can cause runny nose, headache and sore throat.
  • The two-week window. It takes about two weeks for the flu shot to take full effect. If you're exposed to the influenza virus shortly before or during that time period, you might catch the flu.
  • Mismatched flu viruses. In some years, the influenza viruses used for the vaccine don't match the viruses circulating during the flu season. If this occurs, your flu shot won't protect you.
  • Other illnesses. Many other diseases, such as the common cold, also produce flu-like symptoms. So you may think you have the flu when you actually don't.

What kind of protection does the flu vaccine offer?

Flu vaccines aren't 100 percent effective. According to the CDC, when the match between flu vaccine and circulating strains of flu virus is close, a flu shot is between 70 and 90 percent effective in warding off influenza in healthy people under age 65.

Can I lower my risk of the flu without getting a flu shot?

With or without a flu shot, you can take steps to help protect yourself from the flu and other viruses. Good hygiene remains your primary defense against contagious illnesses.

  • Wash your hands often and thoroughly with soap and water.
  • Use an alcohol-based sanitizer on your hands.
  • Avoid touching your eyes, nose or mouth whenever possible.
  • Avoid crowds when the flu is most prevalent in your area.
Last Updated: 2011-08-27
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