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Today’s vaccines use only the ingredients they need to be safe and effective.
A note on vaccine safety
Vaccines go through many years of safety and effectiveness testing. The Food and Drug Administration (FDA) looks at the results of these tests to decide whether to license the vaccine for use in the United States. Learn more about vaccine safety.
Each ingredient in a vaccine serves a specific purpose. For example, vaccine ingredients may:
Vaccines include ingredients to help your immune system respond and build immunity to a specific disease. For example:
Some ingredients help make sure a vaccine continues to work like it’s supposed to and that it stays free of outside germs and bacteria. For example:
Some ingredients that are needed to produce the vaccine are no longer needed for the vaccine to work in a person.
These ingredients are taken out after production so only tiny amounts are left in the final product. The very small amounts of these ingredients that remain in the final product aren’t harmful.
Examples of ingredients used in some vaccines include:
Learn more about the types of vaccine ingredients and why they’re used from the common questions below.
A: No. Thimerosal has a different form of mercury (ethylmercury) than the kind that causes mercury poisoning (methylmercury). It’s safe to use ethylmercury in vaccines because it’s less likely to build up in the body — and because it’s used in very, very small amounts. Even so, most vaccines do not have any thimerosal in them. If you’re concerned about thimerosal or mercury in vaccines, talk with your doctor.
A: Yes. However, if you have an allergy to antibiotics, it’s a good idea to talk with your doctor about getting vaccinated. But in general, antibiotics that people are most likely to be allergic to — like penicillin — aren’t used in vaccines.
A: Yes. People with egg allergies can get any licensed, recommended flu vaccine that’s appropriate for their age. They no longer have to be watched for 30 minutes after getting the vaccine. People who have severe egg allergies should be vaccinated in a medical setting and be supervised by a health care professional who can recognize and manage severe allergic conditions.
A: No. If formaldehyde is used to help produce a vaccine, only very small amounts are left in the final product. This amount is so small that it’s not dangerous — in fact, there’s actually more formaldehyde found naturally in our bodies than there is in vaccines made with formaldehyde.
A: No. Vaccines made with aluminum have only a very small amount of aluminum in them. For decades, vaccines that include aluminum have been tested for safety — these studies have shown that using aluminum in vaccines is safe.
Last reviewed: December 2017