FAQs About the Seasonal Flu Vaccine
- What is flu vaccine?
- Who should get flu vaccine and when?
- Who should not get the flu vaccine? Who should proceed with caution?
- What are the side effects of the flu vaccine?
What is flu vaccine?
The standard flu vaccine (or, the "flu shot") is made from flu viruses that have been grown on fertilized chicken eggs. The viruses are killed during manufacturing, a process known as “inactivation.” These inactivated viruses are a source of proteins or antigens that trigger a protective antibody response when the vaccine is injected into the arm or thigh muscle. Antibodies against flu viruses begin to appear one to two weeks after getting the flu shot and last for months, and sometimes even up to one year.
The standard flu shot is the main flu vaccine that will be offered at PAMF for the 2015-2016 season.
Three other flu vaccines will also be available to certain patients:
1) FluMist nasal spray vaccine:
FluMist, an intranasal vaccine, is available to patients 2-49 years of age who have no contraindications to it.
2) Fluzone High-Dose:
Fluzone High-Dose vaccine, a flu shot with four times the antigen dose per strain as standard flu vaccine, is approved only for persons 65 years of age or older.
Flublok is a recombinant flu vaccine manufactured without the use of eggs. It is indicated for highly egg-allergic persons aged 18 years or older. It is available only in our allergy departments.
PAMF has transitioned from trivalent to quadrivalent flu vaccines (containing 2 A strains and 2 B strains) with the exception of Fluzone High-Dose and Flublok which are still trivalent (2 A strains and 1 B strain). The second B strain was added to quadrivalent vaccines by manufacturers because predicting which flu B strain would circulate in any given season proved difficult. While this is a modest change, scientists hope it will result in increased protection against the flu in coming years. The higher dose of antigen in Fluzone High-Dose vaccine produces higher antibody levels in patients 65 years or older which results in a modest boost in effectiveness compared to the standard-dose vaccine.
Because vaccine strains often change from one year to the next and immunity wanes, flu vaccine must be given every year.
All flu vaccines at PAMF will be Thimerosal-free and latex-free.
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Who should get flu vaccine and when?
The easy answer is that almost everyone 6 months of age and older should get the flu vaccine. They should get the vaccine in September or October, but they can be vaccinated throughout the flu season. Special efforts should be made to vaccinate the following persons because they are either at risk for complications from the flu, or they might give the flu to someone who is at risk:
- Women who are or will be pregnant during the flu season - the World Health Organization places a very high priority on vaccinating pregnant women
- Children younger than 5 years, especially children under age 2
- Children on chronic aspirin therapy
- People 50 years and older
- Persons who are morbidly obese
- Native American and Alaskan natives
- Persons of any age with certain chronic medical conditions
- Persons who live in nursing homes and other long-term care facilities
- Persons 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? Who should proceed with caution?
Flu vaccine is extremely safe for the vast majority of persons, including breastfeeding and pregnant women (pregnant women should receive the flu shot, but should not get the FluMist nasal spray vaccine). However, some groups should exercise caution:
- Persons with a history of severe allergic reaction to the flu vaccine should not get the flu vaccine.
- Persons with a severe allergy to eggs should consult an allergist. (Flubok may be considered if the patient is 18 years of age or older.)
- Persons with milder allergic reactions to eggs (such as hives only) should speak with their vaccine or health care provider first. (Usually the standard flu shot can be administered, followed by 30 minutes of observation, or the Flublok vaccine, which is not egg-based, can be given by an allergist if the patient is 18 years of age or older.)
- Anyone with moderate to severe acute illness should delay flu vaccination until resolution of the illness.
- Children under 6 months of age should not get the flu vaccine because it is ineffective in this age group (instead, their household contacts and caretakers should get vaccinated).
- Persons with a history of Guillain-Barre syndrome should consult their doctor before receiving the flu vaccine.
- Note: The nasal spray vaccine, FluMist, has in addition the following specific contraindications: current use of aspirin (in children 2-17 years), pregnancy, immunosuppressed state, egg allergy of any kind, asthma history or wheezing within 12 months in children 2-4 years, antiviral medication within the last 48 hours, or caring for severely immunosuppressed persons (e.g. bone-marrow transplant). Precautions are also cited by the manufacturer for age > 5 years with asthma, chronic medical conditions.
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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. Moreover, influenza itself is known to cause GBS and flu vaccine may be protective. However, anyone who has had GBS within six weeks of flu vaccination should speak with their physician first before receiving flu vaccine.
For more information, visit the CDC website and these pages on the PAMF flu website:
Children and Flu Vaccine
High-Dose Flu Vaccine
Pregnancy and the Flu
Last updated 8/2015
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- Health care workers