Influenza (Flu) Immunization Information

What is influenza (flu)?
How does flu immunization work?
How effective are they?
Any side effects?
Should I get one, and which should I get?
When should I get one?
Helpful links

What is influenza (flu)?

Influenza is caused by a virus that causes an upper respiratory infection. Unlike most colds, however, the flu often causes fever, muscle aches, and dizziness. It can also lead to more serious infections, such as pneumonia. Complications from flu cause up to 40,000 deaths per year in the U.S. These deaths usually occur in the elderly and in people with chronic health problems, such as heart disease and severe asthma.

The influenza virus is always present somewhere in the world. In the United States flu outbreaks tend to occur each year between November and March.

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How does flu immunization work?

The formula for the flu vaccine is changed every year according to the recommendations of scientists from the Centers for Disease Control (CDC). They predict which strains of flu virus are most likely to appear the next winter.

1. Flu shot: The virus in the flu vaccine has been inactivated, or "killed." This means you cannot catch the flu from getting a shot. Getting the shot introduces part of the flu virus to your immune system. Your body then reacts by making protective antibodies against the virus.

2. FluMist: The virus in this nasal spray has been weakened (attenuated).  The virus replicates in your body and produces antibodies (and thus immunity) to influenza.

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How effective are they?

Immunization typically is about 70% effective in preventing the flu. Even if you do get the flu, the vaccine helps protect against severe infection. For this reason it is said that the flu shot protects against death from the flu more than from flu itself.

Immunization will not protect against colds and other infections.  "The flu" is a specific illness.

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What are the side effects?

1. Flu Shot:
   Eggs are used in the production of flu vaccine. If you are allergic to eggs, you may have a severe allergic reaction to the flu shot. The flu shot should not be taken by anyone who has a history of severe egg allergy. 
   
   Some manufacturers also recommend not getting a flu shot if you have an allergy to thimerosal. Thimerosal is a preservative used in contact lens solutions and the flu vaccine.
   
   For people who do not have egg or thimerosal allergies, the flu vaccine has infrequent, minor side effects. The most common reaction is some soreness at the site of the shot. A few people develop fever or muscle aches within a few hours of the injection. These symptoms may last 1 to 2 days.
   
   There have been no reports of flu shot complications affecting the nervous system since the 1976-1977 swine flu epidemic.
   
2. FluMist - most people have no side effects or very mild ones.  The following list has been reported.
   a. Allergy - those allergic to eggs should not take.
   b. Runny nose
   c. Headache
   d. Sore throat
   e. Fatigue
   f. Muscle aches
   g. Cough
   h. Chills
   i. Low grade fever
   
   More FluMist Information

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Should I get one, and which should I get?

Flu Shot Only:

• people over the age of 50
• people whose immune systems may be impaired, such as by HIV, cancer, or an organ transplant
• people with chronic medical problems, such as asthma or reactive airway disease, heart disease, emphysema, and diabetes
• Women who expect to be in 2nd or 3rd trimester of pregnancy during the flu season (November-March)

Flu Shot OR FluMist:

• people working in health care
• school teachers and other community workers with close, daily contact with the public
• others who wish to decrease their chance of catching the flu (thus almost anyone)

Should NOT get FluMist:

• all those listed in first group above
• people with an illness with fever or a respiratory illness (until 3 days after symptoms have resolved)
• people with a history of Guillen-Barre disease
• pregnant women
• people who may come into close contact (e.g., live in same house/room with) with immunocompromised individuals for 3 weeks following vaccination

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When should I get one?

We recommend receiving immunization around the end of October or the beginning of November.  However, it is possible to receive benefit from the vaccine through the winter.

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Helpful Links

• Center for Disease Control flu information page
• New Jersey Department of Health flu information page
• Immunization Action Coalition - a good detailed site for flu and other immunizations
• Intelihealth - a good, general medical site for public use

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Last Modified 02/06/2007