What's in the flu vaccine?
Breaking down the flu vaccine
Thimerosal is a form of mercury used as a preservative in some multi-dose vials of the flu vaccine. Most flu vaccines are given from single-dose vials and do not contain mercury. Thimerosal is different than the mercury that causes mercury poisoning, and our bodies process it easily.
Formaldehyde is used to eliminate viruses and toxins in the manufacturing of some flu vaccines. However, the amount used is smaller than the amount found naturally in the human body, and it's not known to be dangerous.
Some flu vaccines contain a small amount of egg protein. This should not stop individuals with egg allergies from getting their flu shot. If you have an egg allergy, you can get a flu vaccine without egg protein.