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Home > Health Information > Health Library > Influenza (Flu) Vaccine (Inactivated or Recombinant): What You Need to Know
Influenza ("flu") is a contagious disease that spreads around the United States every winter, usually between October and May.
Flu is caused by influenza viruses and is spread mainly by coughing, sneezing, and close contact.
Anyone can get flu. Flu strikes suddenly and can last several days. Symptoms vary by age, but can include:
Flu can also lead to pneumonia and blood infections, and cause diarrhea and seizures in children. If you have a medical condition, such as heart or lung disease, flu can make it worse.
Flu is more dangerous for some people. Infants and young children, people 65 years of age and older, pregnant women, and people with certain health conditions or a weakened immune system are at greatest risk.
Each year thousands of people in the United States die from flu, and many more are hospitalized.
Flu vaccine can:
A dose of flu vaccine is recommended every flu season. Children 6 months through 8 years of age may need two doses during the same flu season. Everyone else needs only one dose each flu season.
Some inactivated flu vaccines contain a very small amount of a mercury-based preservative called thimerosal. Studies have not shown thimerosal in vaccines to be harmful, but flu vaccines that do not contain thimerosal are available.
There is no live flu virus in flu shots. They cannot cause the flu.
There are many flu viruses, and they are always changing. Each year a new flu vaccine is made to protect against three or four viruses that are likely to cause disease in the upcoming flu season. But even when the vaccine doesn't exactly match these viruses, it may still provide some protection.
Flu vaccine cannot prevent:
Tell the person who is giving you the vaccine:
With any medicine, including vaccines, there is a chance of reactions. These are usually mild and go away on their own, but serious reactions are also possible.
Most people who get a flu shot do not have any problems with it.
Minor problems following a flu shot include:
If these problems occur, they usually begin soon after the shot and last 1 or 2 days.
More serious problems following a flu shot can include the following:
Problems that could happen after any injected vaccine:
As with any medicine, there is a very remote chance of a vaccine causing a serious injury or death.
The safety of vaccines is always being monitored. For more information, visit: www.cdc.gov/vaccinesafety/.
Signs of a severe allergic reaction can include hives, swelling of the face and throat, difficulty breathing, a fast heartbeat, dizziness, and weakness – usually within a few minutes to a few hours after the vaccination.
VAERS does not give medical advice.
The National Vaccine Injury Compensation Program (VICP) is a federal program that was created to compensate people who may have been injured by certain vaccines.
Persons who believe they may have been injured by a vaccine can learn about the program and about filing a claim by calling 1-800-338-2382 or visiting the VICP website at www.hrsa.gov/vaccinecompensation. There is a time limit to file a claim for compensation.
Vaccine Information Statement
Inactivated Influenza Vaccine
42 U.S.C. § 300aa-26
Department of Health and Human Services
Centers for Disease Control and Prevention
Many Vaccine Information Statements are available in Spanish and other languages. See www.immunize.org/vis.
Muchas hojas de información sobre vacunas están disponibles en español y en otros idiomas. Visite www.immunize.org/vis.
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