Influenza Vaccine: An Overview
The main way to keep from getting
the flu is to get a yearly
influenza vaccine. You can get the vaccine at:
- Your doctor's office
- A local clinic
- Work (in many communities)
- Supermarkets
- Drugstores.
It is important to note that you must get the influenza vaccine every year because the viruses on which it is based change every year.
How the Influenza Vaccine Is Made
Scientists make a different influenza vaccine every year because the strains of flu viruses change from year to year. Nine to ten months before the flu season begins, scientists prepare a new influenza vaccine made from inactivated (killed) flu viruses. Because the viruses are killed, they cannot cause infection. The influenza vaccine preparation is based on the flu viruses that are in circulation at the time and on the viruses that are expected to circulate the following winter.
It is important to note that an unpredicted new strain of the flu virus may appear after the influenza vaccine has been made and distributed to doctors' offices and clinics. This means that even if you do get the influenza vaccine, you still may get infected. However, if this happens, the disease is usually milder because the influenza vaccine will still give you some protection.
(Click Flu Virus for more information about flu viruses.)
Types of the Influenza Vaccine
Until recently, you could get the
influenza vaccine only as an injection (
flu shot). However, in 2003, the U.S. Food and Drug Administration (FDA) approved a nasal spray form of the influenza vaccine called FluMist
®, which you can get from your healthcare provider. The FDA approved it for use in healthy people who are 5 to 49 years of age.
You should not use FluMist if:
- You have certain lung conditions, including asthma, or heart conditions
- You have metabolic disorders, such as diabetes or kidney dysfunction
- You have an immunodeficiency disease or you are on immunosuppressive treatment
- You have had Guillain-Barré syndrome
- You are pregnant
- You have a history of allergy or hypersensitivity to any of the parts of FluMist or to eggs
- You are a child or teenager who regularly takes aspirin or products containing aspirin.
When Should I Get the Influenza Vaccine?
Your immune system takes time to respond to the influenza vaccine. Therefore, you should get vaccinated 6 to 8 weeks before flu season begins in November to prevent getting infected or to reduce the severity of flu if you do get it. However, flu season usually lasts until March, so it is not too late to get the influenza vaccine after the season has begun. The influenza vaccine itself cannot cause
the flu, but you could become exposed to the virus by someone else and get infected soon after you are vaccinated.
Side Effects of the Influenza Vaccine
Approximately 5 percent to 10 percent of people who get the
influenza vaccine will have mild side effects for about a day after vaccination. The most common side effect in children and adults is soreness at the site of the vaccination. Other side effects, especially in children who previously have not been exposed to the
flu virus, include:
These side effects of the influenza vaccine may begin 6 to 12 hours after vaccination and may last for up to 2 days.
Viruses used for producing the influenza vaccine are grown in chicken eggs and then killed with a chemical so that they can no longer cause an infection. As a result, the influenza vaccine may contain some egg protein, which can cause an allergic reaction. If you are allergic to eggs or have ever had a serious allergic reaction to the influenza vaccine, the Centers for Disease Control and Prevention (CDC) recommends that you consult with your healthcare provider before getting vaccinated.
Who Should Get the Influenza Vaccine?
People who are in any of the following groups, or live in a household with someone who is, should get the influenza vaccine:
- You are 50 years of age or older
- You have chronic diseases of your heart, lungs, or kidneys
- You have diabetes
- Your immune system does not function properly
- You have a severe form of anemia
- You will be more than 3 months pregnant during the flu season
- You live in a nursing home or other chronic-care housing facility
- You are in close contact with children 23 months of age or younger.
The CDC recommends that children 6 months to 23 months of age get the influenza vaccine. Children and teenagers (2 to 18 years of age) should get the influenza vaccine if they are taking long-term aspirin treatment, as they may be at risk of developing Reye's syndrome following a flu infection. Children should also get the influenza vaccine if they live in a household with someone in the above-mentioned groups. Healthcare providers and volunteers should get the influenza vaccine if they work with people in any of these groups.
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