As a parent, it’s smart to question and be aware of anything that goes into your child’s body. Many parents naturally have questions about ingredients in vaccines, specifically when they hear words such as aluminum, formaldehyde, thimerosal, gelatin and antibiotics. However, parents can be reassured that ingredients in vaccines are minuscule, safe and necessary.

Ingredients in vaccines are all there for a reason – to help the vaccine work better and to keep the vaccine safe. Common ingredients in vaccines are:

  • Adjuvants: Adjuvants (like aluminum) help vaccines work better. They enhance the immune response, decreasing the quantity of vaccine needed to gain protective immunity, or lowering the number of doses required.
  • By-products: Some products (like formaldehyde) are used during vaccine manufacturing to make sure viruses are inactivated and are removed except for a tiny trace.
  • Stabilizers: Stabilizers (like gelatin) are added to vaccines to protect the active ingredients from breaking down during manufacture, transport and storage.
  • Preservatives: Preservatives (like trace amounts of thimerosal) prevent bacterial or fungal contamination. Early in the 20th century, most vaccines were packaged in vials that contained multiple doses. Doctors and nurses would draw up a single dose and place the vaccine back in the refrigerator. Unfortunately, sometimes bacteria would inadvertently enter the vial and cause infections. Preservatives, originally added in the 1930s, solved this problem.

Aluminum: Aluminum is present in our environment; the air we breathe, the water we drink and the food we eat all contain aluminum. The average person takes in an estimated 30 to 50 milligrams of aluminum every day, mainly from foods, drinking water, and medicines. Not all vaccines contain aluminum, but those that do typically contain about .125 milligrams to .625 milligrams per dose, or roughly 1 percent of the daily amount we all take in naturally.

For example, in the first six months of life, babies receive about 4 milligrams of aluminum if they get all of the recommended vaccines. However, during this same period they will be exposed to about 10 milligrams of aluminum if they are breastfed, 40 milligrams if they are fed regular infant formula, and up to 120 milligrams if they are fed soy-based infant formula.

Aluminum salts have been used as adjuvants in vaccines in the United States since the 1930s.  Adjuvants enhance the immune response by allowing for lesser quantities of active ingredients and, in some cases, fewer doses.

Some people wonder about the difference between aluminum injected in vaccines versus aluminum ingested in food. Typically, infants have between 1 and 5 nanograms (billionths of a gram) of aluminum in each milliliter of blood. Researchers have shown that after vaccines are injected, the quantity of aluminum detectable in an infant’s blood does not change and that about half of the aluminum from vaccines is eliminated from the body within one day.

See more information on aluminum in vaccines.

Formaldehyde: Vaccines contain antigens, or inactive versions of the viruses or bacteria they are protecting against. Formaldehyde is used during the manufacture of some vaccines to make sure these viruses or bacteria are dead. While most formaldehyde is purified away, small amounts remain. It is important to realize that formaldehyde is also a natural by-product of processes in our bodies, so it is commonly found in the bloodstream. The quantity of formaldehyde found in our blood is 10 times greater than that found in any vaccine.

Thimerosal: Thimerosal, a mercury-containing preservative, is no longer used as a preservative in any childhood vaccine except for the influenza vaccine, and some versions of the influenza vaccine are thimerosal free. Mercury is a naturally occurring element found in the earth’s crust, air, soil and water. As a result, we are all exposed to mercury. Thimerosal is also found in trace amounts in some multi-dose preparations of the influenza vaccines as a preservative to help prevent the vaccine from becoming contaminated with bacteria, which could cause infection.

Today, breastfed infants are exposed to 15 times more mercury in breast milk than is contained in the influenza vaccine.

More information on thimerosal is available from the Centers for Disease Control and Prevention and the Children’s Hospital of Philadelphia.

Other ingredients: The amount of good and bad information online about vaccines can be overwhelming and confusing, but you can’t believe everything you read about ingredients in vaccines. For example, no vaccine contains, or has ever contained, antifreeze.

It’s important to look to the most trusted physician, research, and public health organizations in the world for answers. The Centers for Disease Control and Prevention has compiled into a table the ingredient list for most vaccines. While the table may be helpful for people concerned about particular allergies or ingredients, it is important to realize that the table does not indicate quantities in each vaccine. In most cases, the quantities are so small that they do not cause allergic reactions or symptoms of toxicity. Talk to your child’s doctor about any questions or concerns you have about vaccine ingredients.

CDC: Ingredients of Vaccines Fact Sheet
CDC: Parents’ Guide to Childhood Immunizations FAQ
Children’s Hospital of Philadelphia: Vaccine Ingredients Q&A