FAQ – Ingredients and Common Concerns
What ingredients are in vaccines?
Vaccine ingredients vary by vaccine, but most include:
- Antigen: the part that teaches your immune system what to recognize
- Adjuvant (in some vaccines): helps create a stronger immune response
- Stabilizers (in some vaccines): help protect the vaccine during storage
You can find the ingredient list in the Vaccine Information Statement (VIS) or the package insert for each vaccine.
Why are there “extra” ingredients besides the active part?
They help the vaccine work well and stay safe and effective during shipping and storage. These ingredients are used in very small amounts and are part of how vaccines are designed to be reliable and consistent.
What is an adjuvant, and why is aluminum used?
An adjuvant helps your immune system respond better, so you may need fewer doses or get stronger protection. Some vaccines use small amounts of aluminum salts, which have been used for decades and are also found in food and water.
Do vaccines contain mercury?
Most routine vaccines do not contain mercury. A preservative called thimerosal (which contains a type of mercury) has been removed from, or reduced to trace amounts in, most vaccines for many years. Some multi-dose flu vials may still contain it, and thimerosal-free options are available.
Do vaccines contain formaldehyde?
Some vaccines can contain very small residual amounts of formaldehyde from the manufacturing process. Your body naturally makes and uses formaldehyde as part of normal metabolism, and the amount in vaccines is tiny.
Do vaccines contain fetal tissue?
No. Some vaccines are made using lab-grown cell lines that originally came from pregnancies that ended decades ago. These cells help produce the vaccine, but the final vaccine does not contain fetal tissue. If you have concerns, please talk with your health care provider about alternative options.
Do vaccines contain gelatin or other animal products?
Some vaccines contain gelatin, which helps protect the vaccine during storage. If you have dietary or religious concerns, check the vaccine’s ingredients list or ask your provider which brands or alternatives are available.
Do vaccines contain eggs?
Some influenza vaccines are made using eggs, while others are not. If you have an egg allergy, talk with your health care provider. Many people with egg allergy can still receive flu vaccine safely, and egg-free options may be available.
Do vaccines contain latex?
Some vaccine packaging (like vial stoppers or syringe components) may contain latex, depending on the product. If you have a latex allergy, tell your provider so they can select an appropriate product.
Do vaccines change your DNA?
No. Vaccines do not change your DNA. Some newer vaccines use mRNA to give your cells instructions to make a harmless piece of a germ so your immune system can learn it. The mRNA does not enter the part of the cell where DNA is kept and it breaks down quickly.
Do vaccines contain “toxins”?
Vaccines can include ingredients with long chemical names, but that does not mean they are harmful at the amounts used. Safety depends on dose, and vaccine ingredients are used in very small amounts that are studied for safety.
Do vaccines overload the immune system?
No. Babies and children are exposed to many new germs every day through normal life. The immune system can respond to many challenges at once. The recommended schedule is designed to protect children as early as possible, when they are at higher risk from certain infections.
Do vaccines cause autism?
No. Vaccines do not cause autism. Autism begins to develop early in life, and signs often become noticeable around the same ages when children receive vaccines. Many studies have looked for a link and have not found one.
Why do people feel worried about ingredients?
People often worry because ingredient names can sound unfamiliar, and misinformation can make them seem scary. If you’re concerned, check the ingredient list for that specific vaccine and talk with a health care provider about what each ingredient does and why it’s there.
What if I have a severe allergy or I reacted to a vaccine before?
Tell your health care provider before getting vaccinated. Most people with allergies can still be vaccinated safely, but a history of a serious allergic reaction may change which vaccines are recommended or where you should receive them.