Why get vaccinated?

Influenza (''flu'') is a contagious disease. It is caused by the influenza virus, which spreads from infected persons to the nose or throat of others. Other illnesses can have the same symptoms and are often mistaken for influenza. But only an illness caused by the influenza virus is really influenza.

Anyone can get influenza, but rates of infection are highest among children. For most people, it lasts only a few days. It can cause: fever, sore throat, chills, fatigue, cough, headache, and muscle aches.

Some people get much sicker. Influenza can lead to pneumonia and can be dangerous for people with heart or breathing conditions. It can cause high fever and seizures in children. On average, 226,000 people are hospitalized every year because of influenza and 36,000 die - mostly elderly.

Influenza vaccine can prevent influenza.

Inactivated Influenza vaccine

There are two types of influenza vaccine:

• An inactivated (killed) vaccine, or ''flu shot,'' is given by injection into the muscle.
• Live, attenuated (weakened) influenza vaccine, called LAIV, is sprayed into the nostrils. This vaccine is described in a separate monograph.

For most people influenza vaccine prevents serious influenzarelated illness. But it will not prevent ''influenza-like'' illnesses caused by other viruses.

Influenza viruses are always changing. Because of this, influenza vaccines are updated every year, and an annual vaccination is recommended. Protection lasts up to a year.

It takes about 2 weeks for protection to develop after the vaccination.

Some inactivated influenza vaccine contains thimerosal, a preservative that contains mercury. Some people believe thimerosal may be related to developmental problems in children. In 2004 the Institute of Medicine published a report concluding that, based on scientific studies, there is no evidence of such a relationship. If you are concerned about thimerosal, ask your doctor about thimerosal-free influenza vaccine.

Who should get inactivated influenza vaccine?

People 6 months of age and older can receive inactivated influenza vaccine. It is recommended for anyone who is at risk of complications from influenza or more likely to require medical care:

• All children from 6 months up to 5 years of age.
• Anyone 50 years of age or older.
• Anyone 6 months to 18 years of age on long-term aspirin treatment (they could develop Reye Syndrome if they got influenza).
• Women who will be pregnant during influenza season.
• Anyone with long-term health problems with heart disease; kidney disease; lung disease; metabolic disease, such as diabetes; asthma; anemia, and other blood disorders.
• Anyone with a weakened immune system due to HIV/AIDS or other diseases affecting the immune system; long-term treatment with drugs such as steroids; cancer treatment with x-rays or drugs.
• Anyone with certain muscle or nerve disorders (such as seizure disorders or severe cerebral palsy) that can lead to breathing or swallowing problems.
• Residents of nursing homes and other chronic-care facilities.

Influenza vaccine is also recommended for anyone who lives with or cares for people at high risk for influenzarelated complications:

• Health care providers.
• Household contacts and caregivers of children from birth up to 5 years of age.
• Household contacts and caregivers of people 50 years and older, and those with medical conditions that put them at higher risk for severe complications from influenza.

A yearly influenza vaccination should be considered for:

• People who provide essential community services.
• People living in dormitories or under other crowded conditions, to prevent outbreaks.
• People at high risk of influenza complications who travel to the Southern hemisphere between April and September, or to the tropics or in organized tourist groups at any time.

Influenza vaccine is also recommended for anyone who wants to reduce the likelihood of becoming ill with influenza or spreading influenza to others.

When should I get influenza vaccine?

Plan to get influenza vaccine in October or November if you can. But getting vaccinated in December, or even later, will still be beneficial in most years. You can get the vaccine as soon as it is available, and for as long as illness is occurring. Influenza illness can occur any time from November through May. Most cases usually occur in January or February.

Most people need one dose of influenza vaccine each year. Children younger than 9 years of age getting influenza vaccine for the first time should get 2 doses. For inactivated vaccine, these doses should be given at least 4 weeks apart.

Influenza vaccine may be given at the same time as other vaccines, including pneumococcal vaccine.

How can I learn more?

• Ask your doctor or other health care provider. They can give you the vaccine package insert or suggest other sources of information.
• Call your local or state health department's immunization program.
• Contact the Centers for Disease Control and Prevention (CDC): call 1-800-232-4636 (1-800-CDC-INFO) or visit the National Immunization Program's website at http://www.cdc.gov/vaccines.

Inactivated Influenza Vaccine Information Statement. U.S. Department of Health and Human Services/Centers for Disease Control and Prevention National Immunization Program. 7/16/2007.

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