What to know
Modern vaccines contain only the ingredients that are needed for the vaccines to be as safe and effective as possible.
Every vaccine ingredient serves a purpose
To provide immunity
We become immune to (or protected from) a disease when our bodies create specific antibodies to fight that disease. Vaccines contain ingredients that help your body build this immunity.
To keep the vaccine safe and long-lasting
Vaccines need to be safe and effective. Certain ingredients help keep vaccines safe from contamination and toxins. Others, like stabilizers, help vaccines stay effective for a long time.
To make the vaccine more effective
All vaccine ingredients help to make a vaccine as effective as possible, while being safe. Ingredients like aluminum salt help boost the body's response to the vaccine.
Ingredients found in some vaccines
Stabilizers
- Purpose: To keep the vaccine effective after manufacturing
- Most commonly found in: Jell-O®, naturally in the body
- Examples: Sugars, gelatin
Adjuvants
- Purpose: To help boost the body's response to the vaccine
- Most commonly found in: Drinking water, infant formula, and some health products such as antacids, buffered aspirin, and antiperspirants
- Examples: Aluminum salts
Residual inactivating ingredients
- Purpose: To kill viruses or inactivate toxins during the manufacturing process
- Most commonly found in: Naturally in the human body, fruit, household furnishings (carpets, upholstering)
- Example: FormaldehydeA
Residual cell culture materials
- Purpose: To grow enough of the virus or bacteria to make the vaccine
- Most commonly found in: Eggs, and foods that contain eggs
- Examples: Egg proteinB
Residual antibiotics
- Purpose: To prevent contamination by bacteria during the vaccine manufacturing process
- Most commonly found in: Common antibiotics. Antibiotics that people are most likely to be allergic to—like penicillin—aren't used in vaccines.
- Examples: Neomycin, Kanamycin, Streptomycin
Preservatives
- Purpose: To prevent contamination
- Most commonly found in: Some kinds of fish
- Example: ThimerosalC (only in multi-dose vials of flu vaccine)
Most vaccines don't contain any mercury
Most vaccines do not have any mercury in them. However, multi-dose flu vaccines and one type of tetanus-diphtheria (Td) vaccine contain a small amount of thimerosal. Thimerosal contains a form of mercury (ethylmercury) that does not cause mercury poisoning and is safe for use in vaccines. Flu and Td vaccines are also available in thimerosal-free versions.
Different types of vaccines work in different ways
Ingredients in specific vaccines
The Food and Drug Administration (FDA), which is responsible for making sure vaccines are safe and effective, has information about all approved vaccines. Check out the below links to discover the different vaccine options and the various ingredients.
Learn about the vaccines that are currently approved in the U.S. by the FDA to prevent different diseases.
Want to know more? Read about common vaccine ingredients from the FDA.
- Formaldehyde is diluted during the vaccine manufacturing process, but residual quantities of formaldehyde may be found in some current vaccines. The amount of formaldehyde present in some vaccines is so small compared to the concentration that occurs naturally in the body that it does not pose a safety concern.
- Because some influenza and yellow fever vaccines are made in eggs, egg proteins are present in the final products. People with 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. For people with egg allergies, there are also flu vaccines that have been made without using eggs in the manufacturing process.
- Thimerosal contains a different form of mercury (ethylmercury) than the kind that causes mercury poisoning (methylmercury). Ethylmercury is safe to use in vaccines because it's processed differently in the body and is less likely to build up in the body—and because it's used in tiny amounts. Even so, most vaccines do not have any thimerosal in them. Learn more about thimerosal, mercury, and vaccine safety.