From the Guidelines
Vaccines contain several key ingredients, including antigens, adjuvants, preservatives, and stabilizers, which work together to provide immunity against specific diseases, with the most recent evidence suggesting that non-active vaccine ingredients such as formaldehyde, thimerosal, egg protein, and gelatin, as well as polyethylene glycol (PEG) and polysorbate, can trigger allergic reactions 1. The main component of vaccines is the antigen, which is a weakened or inactive form of the disease-causing organism that triggers an immune response without causing illness.
- Vaccines also contain adjuvants like aluminum salts that enhance the immune response,
- preservatives such as phenol or thimerosal (in multi-dose vials) to prevent contamination,
- and stabilizers like sugars or gelatin to maintain effectiveness during storage. Some vaccines contain trace amounts of antibiotics to prevent bacterial growth during manufacturing, and may include small amounts of egg protein or other culture materials used in production. Formaldehyde might be present in minute quantities to inactivate viruses or toxins, though most is removed during purification. These ingredients have been extensively tested for safety and are present in very small amounts, as noted in studies on vaccine components and their potential to cause allergic reactions 1. The specific ingredients vary by vaccine type, but all serve important functions in ensuring vaccines are safe, effective, and can be stored properly until use, with the most recent and highest quality study indicating that ingredients like PEG and polysorbate can trigger IgE formation and mast cell degranulation 1.
From the Research
Vaccine Ingredients
The ingredients in vaccines can vary depending on the type of vaccine and its formulation. Some common ingredients found in vaccines include:
- Aluminum salts, such as aluminum hydroxide or aluminum phosphate, which are used as adjuvants to enhance the immune response 2, 3, 4
- Thimerosal, a mercury-containing preservative that is used in some vaccines to prevent contamination 5
- Live attenuated viruses, such as varicella or vaccinia, which are used in some vaccines to provide immunity against specific diseases 5
- Antigens, such as sugar vaccine targets, which are used to stimulate an immune response against specific diseases 6
Adjuvants in Vaccines
Adjuvants are substances that are added to vaccines to enhance the immune response. Some common adjuvants used in vaccines include:
- Alum (aluminum hydroxide) 2, 3, 4
- MF59 3
- AS03 3
- AS01 3
- Saponins 3
- TLRs agonists 3
- Polysaccharides 3
- Nanoparticles 3
- Cytokines 3
- Mucosal adjuvants 3
Other Ingredients
Other ingredients that may be found in vaccines include: