Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 2004;70(7):1343-1344

What is the flu?

The flu (also called influenza) is an infection in the nose, throat, and lungs that is caused by a virus. About 10 to 20 percent of Americans get the flu each year. Some people get very sick. Each year, about 130,000 people go to a hospital with the flu, and 20,000 people die from it.

The flu may cause fever, cough, sore throat, a runny or stuffy nose, headache, muscle aches, and tiredness. Some people describe the flu as being like the worst cold of their life. Most people feel better after one or two weeks. But in some people, the flu leads to serious, even life-threatening diseases, such as pneumonia. Flu vaccinations are recommended for people who are more likely to get very sick and need to be protected from the flu.

Who is at higher risk for getting the flu?

You have a higher risk of getting very sick from the flu if you:

  • Are 50 years or older

  • Are a health care worker

  • Have a lung problem, such as asthma or emphysema

  • Have a suppressed (weak) immune system

  • Have a problem with your kidneys

  • Have diabetes, heart disease, or other long-term health problems

If you are in any of these groups, you probably should get a flu vaccination every year.

Other people also should get the vaccine because they might spread the flu to high-risk people. You should get vaccinated if you work in a long-term care facility. Even if you are not at higher risk, you may want to get vaccinated so you do not get sick with the flu. Healthy children six months of age and older should get vaccinated.

What is the flu vaccine?

There are two kinds of flu vaccines. The first kind is a shot that contains viruses that have been killed. Your body builds up antibodies to those viruses to protect you from the flu. Then if a “live” virus gets into your body, your defenses are ready. These defenses keep you from getting the flu. You cannot get the flu from the shot because the viruses are dead.

The second kind of vaccine is a liquid that you spray up your nose. The mist contains live viruses. These viruses have been changed so that they do not grow well in your body, but they make your body build up antibodies. Only healthy people five to 49 years of age can use the nasal mist.

Because flu viruses change from year to year, you must get the shot or use the nasal spray each year to be protected.

Can I still get the flu if I get vaccinated?

Yes. Even with a flu vaccination, you may not be completely protected. Each year, the flu vaccine contains three different kinds of flu virus. Scientists choose the types that are most likely to show up in the United States that year. If their choice is right, the vaccine is 70 to 90 percent effective in preventing the flu in healthy people younger than 65 years. If you are older than 65, the vaccine is less likely to prevent the flu. If you get the flu after you are vaccinated, your symptoms should be milder than if you did not get vaccinated. You also will be less likely to get serious problems from the flu.

Is the vaccine safe?

Yes. The flu shot is safe in people older than six months. The shot has few side effects. Your arm may be a little sore for a few days. You may have a fever, feel tired, or have sore muscles for a while.

The nasal spray is safe in people older than five years. People who have asthma, other airway diseases, and immune system diseases should not use the nasal mist. The mist has a few side effects, including runny nose, nasal congestion, sore throat, and cough.

Some people are allergic to the flu vaccine. If you have a severe allergy to eggs, you should not get the shot or use the nasal spray. If you are allergic to eggs, your doctor will tell you if it is OK to get a flu shot or use the nasal spray.

Some pregnant women should not get a flu vaccination. Talk to your doctor if you are pregnant and want to get vaccinated.

Where can I learn more about the flu vaccine?

Your doctor.

Centers for Disease Control and Prevention,

National Immunization Information Hotline

Telephone: 1-800-232-2522 (English) 1-800-232-0233 (Español)

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