• What is influenza?
• Who should get influenza vaccine and when?
• Who should not get the influenza vaccine?
• What are the side effects of the influenza vaccine?
• Is thimerosal safe?
• Is a thimerosal-free vaccine available?

What is influenza?

The standard influenza vaccine, or the "flu shot," is a vaccine made from flu viruses that are grown on fertilized chicken eggs. The viruses are inactivated (killed) during the manufacturing process. The inactivated viruses are a source of proteins known as antigens that trigger a protective antibody response when injected into the arm or thigh muscle. Protective antibodies begin to appear one to two weeks after receiving a flu vaccination and last three to six months.

The flu shot must be given every year for two reasons.

First, immunity from the flu vaccine may begin to fade even after several months. (However, the vaccine is usually effective throughout the flu season). After a year passes, a new dose of flu vaccine is necessary to generate immunity again.

Second, the proteins on the surface of flu viruses (which antibodies attack) tend to change from year to year. These antigen changes often require modification of the vaccine to match the most recent strains of flu. The 2008-2009 influenza vaccine contains antigens of the following strains: A/Brisbane/10/2007 (H3N2)-like, A/Brisbane/59/2007 (H1N1)-like, and B/Florida/4/2006-like antigens.

A live, intra-nasal influenza vaccine was introduced in 2003. Its use is limited to healthy persons 2 to 49 years of age. The intranasal vaccine is generally as effective as the flu shot but may cause symptoms of a mild upper respiratory infection.
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Who should get influenza vaccine and when?

PAMF divides its flu clinics into "early" and "later" groups. The early clinics are intended for patients who are at a high risk for serious complications from the flu and persons with whom they have close contact. The later clinics are open to all PAMF patients.

Early clinics should include the following patients:

1. High-risk patients:
   • Persons 65 years or older
     
   • Residents of nursing homes or long-term care facilities
     
   • Patients with chronic heart or lung conditions, including asthma, chronic obstructive pulmonary disease (COPD) and heart failure
     
   • Patients with chronic medical conditions such as diabetes, kidney problems, cancer, chemotherapy, long-term steroid treatment, sickle-cell disease or HIV infection
     
   • Women who will be pregnant during the flu season
     
   • Children receiving chronic aspirin therapy
     
   • Individuals with neuro-muscular conditions (such as individuals with multiple sclerosis, Alzheimer’s and spinal cord injuries)
     
   • All children 6 to 59 months of age (both those with high-risk medical conditions and those who are healthy)
2. Household contacts and out-of-home caregivers of high-risk patients (especially children less than 6 months of age)
   
3. Health care workers

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Who should not get the influenza vaccine?

The flu shot is fine for the vast majority of people, including breastfeeding women. However, several groups of people should take caution.

• Persons with a history of severe allergic reaction to eggs or the influenza vaccine should consult a physician before receiving influenza vaccine.
  
• 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 shot because the vaccine is ineffective in this age group.
  
• Persons with a history of Guillain-Barre syndrome should consult their physicians before receiving the flu shot.
  
• The live, intranasal influenza vaccine is restricted to healthy, non-pregnant persons 2 to 49 years of age.

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What are the side effects of the influenza vaccine?

Influenza 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 with the split virus vaccine product used in the United States. The live, intranasal flu vaccine can cause symptoms of a head cold.

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 subsequent flu vaccines and GBS. It is estimated that perhaps one to two excess cases of GBS per million persons vaccinated may be attributable to the flu shot. This extremely low incidence of GBS stands in contrast to the thousands of lives saved among high-risk persons by the flu shot.
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Is thimerosal safe?

Thimerosal, a preservative in the standard flu vaccine (the classic "flu shot"), is considered safe by the CDC (see www.cdc.gov/flu/about/qa/thimerosal.htm). Nonetheless, thimerosal, which contains a minute amount of mercury, has been phased out of routine childhood vaccines. A California state law effective July 1, 2006 mandates the use of influenza vaccine that has zero or trace amounts of thimerosal in two patient groups:

1. Children under 36 months of age
   
2. Pregnant women (see "Is a thimerosal-free vaccine available?")

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Is a thimerosal-free vaccine available?

In accordance with a new state law, PAMF will provide thimerosal-free vaccine for patients who are children 6 to 35 months of age or pregnant women. All other patients will be offered the traditional flu shot. Healthy, non-pregnant individuals 2 to 49 years of age who wish to receive a preservative-free flu vaccine may consider the live, intranasal vaccine at an office visit with their primary care provider or at a local pharmacy.
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