What Is a Preservative-Free Flu Vaccine?

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

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.

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, thimerosal is used as another line of protection.

Back in 1998, a physician 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.

• Learn more about the Vaccines and Autism debate.

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.

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.

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.

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

• Soreness at the injection site
• Low grade fever

• TirednessSide 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.

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

Although there has been no clear evidence that thimerosol is dangerous when it is included in vaccines, there are now many flu vaccine options that do not contain this ingredient. It is used in multi-dose vials but not in single dose injections. If you would like a preservative-free flu vaccine, talk to your health care provider or pharmacist.