Print Now
Close Window

Seasonal Flu Vaccine - Quick Facts

September 18, 2009

INACTIVATED INFLUENZA:  What You Need To Know --  Many Vaccine Information Statements are available in Spanish and other languages. See 2009-10

1. Why get vaccinated?
Infl uenza ("fl u") is a contagious disease. It is caused by the infl uenza virus, which can be spread by coughing, sneezing, or nasal secretions. Other illnesses can have the same symptoms and are often mistaken for infl uenza. But only an illness caused by the infl uenza virus is really influenza. Anyone can get infl uenza, 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 • muscle aches Some people, such as infants, elderly, and those with certain health conditions, can get much sicker. Flu can cause high fever and pneumonia, and make existing medical conditions worse. It can cause diarrhea and seizures in children. On average, 226,000 people are hospitalized every year because of infl uenza and 36,000 die – mostly elderly. Infl uenza vaccine can prevent influenza.
2. Inactivated infl uenza vaccine
There are two types of seasonal infl uenza vaccine:
Inactivated (killed) vaccine, or the"fl u shot" is given by injection into the muscle. 2. Live, attenuated (weakened) infl uenza vaccine is sprayed into the nostrils. This vaccine is described in a separate Vaccine Information Statement.
Infl uenza viruses are always changing. Because of this, these "seasonal" influenza vaccines are formulated to prevent annual fl u. They do not protect against pandemic H1N1 influenza.  Infl uenza vaccines are updated every year, and an annual vaccination is recommended. Each year scientists try to match the viruses in the vaccine to those most likely to cause fl u that year. When there is a close match the vaccine protects most people from serious influenza related illness. But even when there is not a close match, the vaccine provides some protection. Infl uenza vaccine will not prevent "infl uenza-like" illnesses caused by other viruses. It takes up to 2 weeks for protection to develop after the shot. Protection lasts up to a year. Some inactivated infl uenza vaccine contains a preservative called thimerosal. Some people have suggested that thimerosal may be related to developmental problems in children. In 2004 the Institute of Medicine reviewed many studies looking into this theory and concluded that there is no evidence of such a relationship. Thimerosal-free infl uenza vaccine is available.
3. Who should get inactivated influenza vaccine?
Anyone who wants to reduce the likelihood of becoming ill with influenza or spreading infl uenza to others. All children 6 months and older and all older adults: • All children from 6 months through 18 years of age. • Anyone 50 years of age or older. Anyone who is at risk of complications from influenza, or more likely to require medical care: • Women who will be pregnant during infl uenza season. • Anyone with long-term health problems with: -heart disease - kidney disease - liver 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 cerebral palsy) that can lead to breathing or swallowing problems. • Anyone 6 months through 18 years of age on long-term aspirin treatment (they could develop Reye Syndrome if they got influenza). • Residents of nursing homes and other chronic-care facilities. Anyone who lives with or cares for people at high risk for infl uenza-related 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, or -anyone with medical conditions that put them at higher risk for severe complications from influenza. Health care providers may also recommend a yearly influenza vaccination for: • People who provide essential community services. • People living in dormitories, correctional facilities, or under other crowded conditions, to prevent outbreaks. • People at high risk of infl uenza complications who travel to the Southern hemisphere between April and September, or to the tropics or in organized tourist groups at any time.
4. When should I get influenza vaccine?
You can get the vaccine as soon as it is available, usually in the fall, and for as long as illness is occurring in your community. Infl uenza can occur any time from November through May, but it most often peaks in January or February. Getting vaccinated in December, or even later, will still be benefi cial in most years. Most people need one dose of infl uenza vaccine each year. Children younger than 9 years of age getting influenza vaccine for the fi rst time – or who got infl uenza vaccine for the fi rst time last season but got only one dose – should get 2 doses, at least 4 weeks apart, to be protected. Infl uenza vaccine may be given at the same time as other vaccines, including pneumococcal vaccine.
Some people should talk with a doctor before getting influenza vaccine
Some people should not get inactivated infl uenza vaccine or should wait before getting it. • Tell your doctor if you have any severe (life-threatening) allergies. Allergic reactions to infl uenza vaccine are rare. -Infl uenza vaccine virus is grown in eggs. People with a severe egg allergy should not get the vaccine. -A severe allergy to any vaccine component is also a reason to not get the vaccine. -If you have had a severe reaction after a previous dose of infl uenza vaccine, tell your doctor. • Tell your doctor if you ever had Guillain-Barrι Syndrome (a severe paralytic illness, also called GBS). You may be able to get the vaccine, but your doctor should help you make the decision. • People who are moderately or severely ill should usually wait until they recover before getting fl u vaccine. If you are ill, talk to your doctor or nurse about whether to reschedule the vaccination. People with a mild illness can usually get the vaccine.
6.  What Are The Risks From Inactivated Flu Vaccine?
A vaccine, like any medicine, could possibly cause serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small. Serious problems from infl uenza vaccine are very rare. The viruses in inactivated infl uenza vaccine have been killed, so you cannot get infl uenza from the vaccine.
Mild problems: • soreness, redness, or swelling where the shot was given • hoarseness; sore, red or itchy eyes; cough • fever • aches If these problems occur, they usually begin soon after the shot and last 1-2 days.
Severe problems: • Life-threatening allergic reactions from vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the shot. • In 1976, a type of infl uenza (swine fl u) vaccine was associated with Guillain-Barrι Syndrome (GBS). Since then, fl u vaccines have not been clearly linked to GBS. However, if there is a risk of GBS from current flu vaccines, it would be no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe infl uenza, which can be prevented by vaccination.
7. What if there is a severe reaction?
What should I look for? Any unusual condition, such as a high fever or behavior changes. Signs of a severe allergic reaction can include diffi culty breathing, hoarseness or wheezing, hives, paleness, weakness, a fast heart beat or dizziness. What should I do? • Call a doctor, or get the person to a doctor right away. • Tell the doctor what happened, the date and time it happened, and when the vaccination was given. • Ask your provider to report the reaction by fi ling a Vaccine Adverse Event Reporting System (VAERS) form. Or you can fi le this report through the VAERS website at, or by calling 1-800-822-7967. VAERS does not provide medical advice.
8. The National Vaccine Injury Compensation Program
A federal program exists to help pay for the care of anyone who has a serious reaction to a vaccine. For more information about the National Vaccine Injury Compensation Program, call 1-800-338-2382, or visit their website at
9. How can I learn more?
• Ask your provider. They can give you the vaccine package insert or suggest other sources of information. • Call your local or state health department. • Contact the Centers for Disease Control and Prevention (CDC): -Call 1-800-232-4636 (1-800-CDC-INFO) or -Visit CDC’s website at