What goes into our vaccines?

Our Experts at Mary Bridge Children’s Have Answers

Vaccine research and development have been conducted in scientific laboratories in the U.S. and worldwide for over 100 years. Millions of children each year receive safe, effective vaccinations that have been approved by the United States Food and Drug Administration or FDA.

Some parents worry that the ingredients in vaccines may not be safe for children. For example, a common misconception is that vaccines can cause autism, a neurological and behavioral disorder. But thanks to years of scientific research, there is no link between vaccines and autism. 

Learn More About the What & Why of Vaccine Ingredients

Common Vaccine Ingredients

How Is Each
Ingredient Used?

What Is an Example?

Where Is Each Ingredient
Typically Found?


Preservatives keep the vaccine from becoming contaminated with microbes like bacteria or fungus.

Thimerosal is only used in multi-dose vials of flu vaccine and is not in any vaccines given to children. This type of preservative contains a form of mercury. Most vaccines are single-dose and do not contain thimerosal.

Eating certain kinds of fish, such as swordfish, contain small amounts of mercury that can pass into the human body.


Adjuvants help boost the body’s immune response to the vaccine.

Aluminum salts

Aluminum salts are in drinking water, infant formula, antacids, buffered aspirin, and antiperspirants.


Stabilizers protect the active ingredients so that the vaccine remains effective.


Foods like fruit snacks, marshmallows, and gummy bears contain gelatin.


Antibiotics prevent contamination by bacteria during the vaccine manufacturing process.


Antibiotics that people are most commonly allergic to — like penicillin — are not used in vaccines.

Cell Culture Ingredients

Laboratory scientists use cultures to grow a virus or bacteria to make the vaccine.

Egg protein

Eggs, or foods containing eggs

Inactivating ingredients

Inactivating ingredients kill viruses during the manufacturing process


The human body contains a natural form of formaldehyde. The chemical is also in automobile exhaust and household furnishings, such as carpets.

If you have more questions about vaccine ingredients, vaccine safety, or how to get the vaccines your child needs, call Mary Bridge Children’s Immunization Clinic at 253-403-1767.