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Preservative-Free Flu Vaccine

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Updated April 23, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

What Is It?:

The preservative-free flu vaccine is a type of flu vaccine that contains no thimerosal. It comes in a single-dose vial, unlike most flu vaccines that are produced in multi-dose vials.

How Is It Different?:

The preservative-free flu vaccine contains no thimerosal. Other than that, the formulation of the flu vaccine is the same. It contains the same three strains of (killed) influenza virus as all other types of flu vaccines.

What Is Thimerosal and Why is it Used?:

Thimerosal is a mercury-based ingredient that is used as a preservative in the flu vaccine to prevent any growth of bacteria, fungus or germs that could contaminate the vaccine. It is used in multi-dose vials of the flu vaccine because they are used to provide the flu vaccine to multiple people. Although different needles are used for each patient and proper precautions are used to clean the top of the vial before each vaccine is drawn up, the thimerosal is used as another line of protection.

Isn't Thimerosal Dangerous?:

Back in 1998, a doctor in Great Britain published a small study claiming that the MMR vaccine had caused children to develop autism. The study has since been proven to be seriously flawed and subsequent studies have failed to show any link between the MMR vaccine and autism. However, that study set off a firestorm of criticism and led many parents to believe that vaccines - or certain ingredients in the vaccines - may be related to the rise in cases of autism.

One such ingredient that is often blamed is thimerosal. It is a mercury-based preservative used in multi-dose vaccine vials to ensure the vaccine does not become contaminated. Thimerosal has not been used in any vaccine other than the multi-dose flu vaccine since 2001. Although no definitive link between thimerosal and autism has even been found, the FDA and CDC made the decision to eliminate it from all vaccines other than the multi-dose flu vaccine because of the widespread public belief that it could be dangerous to children.

Ongoing reviews of multiple studies and scientific evidence by the FDA, CDC, National Institutes of Health (NIH), American Academy of Pediatrics (AAP), Advisory Commitee on Immunization Practices (ACIP) and National Academy of Sciences' Institute of Medicine continue to show that the use of thimerosal in vaccines is safe and effective.

How Do I Get the Preservative-Free Flu Vaccine?:

If you would prefer not to have a flu vaccine that contains thimerosal for yourself or your children, contact your health care provider to see if they have the preservative-free vaccine available. Most vaccine clinics and pharmacies only have on or two types of the vaccine available (typically the traditional flu vaccine - in the multi dose vial - and the nasal spray vaccine) but your health care provider is more likely to carry more options or be able to order it if you request it ahead of time.

Does the Preservative-Free Vaccine Work Differently?:

No, the preservative-free flu vaccine works in the same way that all other flu vaccines work. It does not contain thimerosal because only one dose of the vaccine is in each vial. Like all flu vaccines, it takes about two weeks after the injection to be effective. If a child under the age of nine is being vaccinated against the flu for the first time, she will need a second dose four weeks after the first dose.

What Are the Side Effects?:

Like all injected flu vaccines, side effects of the preservative-free flu vaccine include:

  • Soreness at the injection site
  • Low grade fever
  • Tiredness

    Side effects are typically mild and resolve within a day or two. If you develop more serious complications such as severe swelling, difficulty breathing or numbness, contact your health care provider or seek medical attention right away.

  • Who Should Not Get the Vaccine?:

    Those who should not get the preservative free flu vaccine include:

    • Anyone with a severe egg allergy
    • Anyone with a history of Guillain-Barre syndrome
    • Anyone with an allergy to any of the ingredients in the flu vaccine
    • Anyone with a significant fever at the time of vaccination
    • Infants under 6 months old

    Sources:

    Thimerosal and 2011-2012 Seasonal Flu Vaccines. Seasonal Influenza (Flu) 18 Aug 11. US Centers for Disease Control and Prevention. 26 Dec 11.

    Seasonal Flu Vaccine. Seasonal Influenza (Flu) 07 Dec 11. US Centers for Disease Control and Prevention. 26 Dec 11.

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    6. Preservative-Free Flu Vaccine - Why It's Different

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