FAQs About the Seasonal Flu Vaccine
- What is flu vaccine?
- Who should get flu vaccine and when?
- Who should not get the flu vaccine?
- What are the side effects of the flu vaccine?
- Is a thimerosal-free vaccine available?
What is flu vaccine?
The standard flu vaccine (the “flu shot”) is made from flu viruses that have been grown on fertilized chicken eggs. The viruses are inactivated (killed) during the manufacturing process. These inactivated viruses are a source of proteins known as antigens that trigger a protective antibody response when the vaccine is injected into the arm or thigh muscle. Antibodies against the flu begin to appear one to two weeks after getting the flu shot and last for at least six to eight months, and perhaps one year. The vaccine protects you against the three strains of seasonal flu that have been circulating most recently. The 2012/2013 vaccine includes the 2009 H1N1 pandemic strain like last year’s vaccine, but this year’s contains new influenza A (H3N2) and influenza B strains.
Because vaccine strains often change from one year to the next and immunity wanes, the flu vaccine must be given every year.
A high-dose flu vaccine for persons 65 years or older will again be available in the 2012-2013 season. Known as Fluzone High-Dose™, it contains four times as much antigen as the standard flu vaccine. Although it boosts the antibody level in seniors more than the standard vaccine, we do not know yet if it is more effective in preventing the flu or its complications. The high-dose vaccine is also slightly more likely to cause injection-site pain and fever.
A live, intranasal flu vaccine called Flumist™ was introduced in 2003. Its use is limited to healthy, non-pregnant persons two to 49 years of age. The intranasal vaccine is generally as effective as the flu shot and may be preferred by patients who want to avoid a shot. However, it may cause symptoms of a mild upper respiratory infection.
A new, “intra-dermal” flu vaccine was marketed for the first time in the 2011/2012 season. It employs a much shorter needle, is injected into the skin, and is approved for persons 18 through 64 years. Post-injection pain is about the same as the standard flu shot, but redness is much more common with the intra-dermal shot. Experience with this vaccine is limited and it will not be available at PAMF this season.
All flu vaccine products for the 2012/2013 season contain the same three influenza virus strains (two A strains and a B strain). In February 2012, the FDA approved a new four-strain flu vaccine (containing a second influenza B strain), but this will not be available until the 2013/2014 season.
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Who should get flu vaccine and when?
The easy answer is that almost everyone should get the flu vaccine, and they should get it preferably in September or October. Since the 2010/2011 flu season, the CDC has recommended annual flu vaccination for all persons 6 months of age and older. In addition, special efforts should be made to vaccinate the following persons because they are risk for complications from the flu or they might expose vulnerable persons to the flu:
- Pregnant women
- Children younger than 5, but especially children younger than 2
- People 65 years and older
- Native American and Alaskan natives
- People of any age with certain chronic medical conditions (see the CDC's website for more information.)
- People who live in nursing homes and other long-term care facilities
- People who live with or care for those at high risk for complications from flu, including:
- Health care workers
- Household contacts of persons at high risk for complications from the flu
- Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated
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Who should not get the flu vaccine?
The flu vaccine is extremely safe for the vast majority of people, including breastfeeding and pregnant women (pregnant women may receive the flu shot but should not receive the intranasal vaccine). However, several groups of people should exercise caution:
- Persons with a history of severe allergic reaction to eggs or the flu vaccine itself should consult a physician before receiving flu vaccine. (According to CDC, if an allergic reaction to eggs is only hives and nothing more serious, a person may receive the flu shot [not the nasal vaccine] if a physician is present who is equipped to treat a serious allergic reaction and the person is observed for at least 30 minutes. More serious reactions require consultation with an allergist before flu vaccination.
- Anyone ill with a fever should wait until the fever has resolved before being vaccinated.
- Children under 6 months of age should not get the flu vaccine because it is ineffective in this age group.
- Persons with a history of Guillain-Barre syndrome should consult their physician before receiving the flu vaccine.
- The live, intranasal flu vaccine is restricted to healthy, nonpregnant persons 2 to 49 years of age.
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What are the side effects of the flu vaccine?
The flu vaccine rarely causes serious adverse effects. The most common reaction to the flu shot is mild soreness at the site of injection which is well tolerated. Flu-like symptoms, such as fever and muscle aches, occasionally occur six to 12 hours after receiving the flu shot and last one to two days. However, these symptoms are very rare. The live, intranasal flu vaccine can cause symptoms of a head cold, and the high-dose flu vaccine is more likely to cause injection-site pain or fever.
Guillain-Barre syndrome (GBS), an acute paralytic illness, was linked to the swine flu vaccine of 1976. Since 1976, studies have failed to show a similar association between flu vaccines and GBS. It is estimated that at most one excess case of GBS per million persons vaccinated may be attributable to the flu vaccine. The extremely low incidence of GBS stands in contrast to the many hospitalizations and deaths prevented by the flu vaccine.
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Is a thimerosal-free vaccine available?
Thimerosal, a preservative used in some flu shot products, is considered safe by the U.S. Centers for Disease Control and Prevention (CDC). However, California state law mandates the use of influenza vaccine that has zero or trace amounts of thimerosal in two patient groups: children under 36 months of age and pregnant women. PAMF will be offering thimerosal-free, latex-free flu vaccine products at all its sites for the 2012/2013 season. The live, intranasal flu vaccine also does not contain thimerosal, but is approved only for healthy, nonpregnant persons two through 49 years of age.
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