What’s in Vaccines?
By Ryan Hassan MD MPH
Key Points
Vaccines contain the minimum amount of ingredients required to trigger a consistent, effective immune response.
All vaccines consist of an active ingredient and stabilizers.
Some vaccines contain an adjuvant like aluminum to create a stronger immune response with fewer side effects.
Multi-dose vaccines contain preservatives like thimerosal to prevent contamination between doses.
Vaccines contain substances that we are naturally exposed to and are known to be safe. Most of the ingredients in vaccines are commonly found in our food, water, and soil.
Vaccines contain four or fewer types of ingredients:
Active Ingredient:
This is the antigen to which your body will create an immune response (or in the case of mRNA vaccines, the mRNA that your body will use to create the antigen).
Stabilizers:
Stabilizers allow the vaccine to be safely transported, stored, and injected into the body. These include salts and sugars that are routinely found in our soil and our foods.
Adjuvants:
Adjuvants are added to some vaccines to help the body create a better immune response to the vaccine. The most common adjuvant in children’s vaccines is aluminum. Aluminum is the third most common element in the earth’s crust and the most common metal in the world. It is found in foods and breast milk. It is a skin irritant that causes the redness we sometimes see after an injection, and it tells the body to pay attention to the vaccine and send more immune cells to create an immune response. Adjuvants like aluminum reduce side effects from vaccines by allowing us to use a smaller amount of antigen to create an effective immune response.
Researchers have shown that, after vaccines are injected, the amount of aluminum detectable in an infant’s blood does not change. Half of the aluminum from vaccines is eliminated from the body within one day. Vaccines that contain aluminum are safe for your child. (Vaccine Ingredients - Aluminum | Children's Hospital of Philadelphia (chop.edu), Vaccine Ingredients: What you should know | The Vaccine Education Center at The Children's Hospital of Philadelphia (wyo.gov))
You can also learn more in our animated video, Why is there aluminum in some vaccines? or in our previous blog posts The Safety of Vaccine Ingredients: Part One (Aluminum) — Boost Oregon, and Aluminum and Asthma — Boost Oregon.
Preservatives:
Preservatives are used for vaccines that come in multi-dose vials. They allow multiple doses from the same vial to be safely administered to different people. There is no preservative in any childhood vaccines except for multi-dose flu vaccines. Thimerosal is the most commonly used preservative in the U.S. Thimerosal is broken down into ethylmercury, which our bodies quickly eliminate through our urine. Ethylmercury from vaccines is safe, unlike the methylmercury found in fish, which can be toxic at high levels. (Vaccine Ingredients – Thimerosal | Children's Hospital of Philadelphia (chop.edu)) Learn more in our previous blog post The Safety of Vaccine Ingredients: Part Two (Mercury) — Boost Oregon.
What About Other Things Found in Vaccines?
In addition to the four types of ingredients above, sometimes very small amounts of other materials from the production process are found in trace amounts in vaccines. These materials are filtered out of the final product, but small amounts may remain. For that reason, the materials are listed in the vaccine “excipient list.” This is similar to the way that some food packages state that they are “made in a facility that processes peanuts.” The peanuts aren’t an ingredient, but people with peanut allergies might still react to the food. Vaccine excipients may include antibiotics used to kill bacteria, formaldehyde to kill viruses, yeast cells used to create proteins, or animal or stem cells used to grow viruses.
These materials are generally more common in our bodies and environments than in vaccines. They are used in the manufacturing of vaccines because they are known to be safe. Learn more in our previous blog post The Safety of Vaccine Ingredients: Part Three (Formaldehyde & Other Ingredients) — Boost Oregon.
If you still have questions about vaccines, please visit https://www.boostoregon.org/info-for-parents for more information, or reach out at info@boostoregon.org. We are always listening.