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Vaccine Components

Vaccines contain antigens that prompt the body to create antibodies. The antibodies fight the germs that cause the disease the vaccine is intended to prevent. In addition to antigens, vaccines contain other ingredients or additives used in the production process. These additional ingredients are used to purify, stabilize and preserve, increase the effectiveness of the vaccines, and create the vaccine.



Vaccine Ingredient Description
Suspending fluid

The liquid that contains the chemicals used during production that kill or weaken the germ for use in vaccines.

Preservatives and stabilizers Substances that ensure the vaccine content and potency remain unchanged. Common preservatives and stabilizers include:
  • Formaldehyde, a stabilizer that kills or inactivates unwanted germs in vaccines.
  • Monosodium glutamate, a stabilizer that protects vaccines from heat, light, humidity or acidity while they are stored.
  • Gelatin, a stabilizer that protects vaccines from heat while they are stored.
Adjuvants Substances used to enhance the effectiveness of the vaccines. Aluminum is the most common adjuvant used in US licensed vaccines.
Residual materials The materials used to grow the virus or bacteria contained within the vaccines. Common residual materials include:
  • Antibiotics which are used during the production of some vaccines to prevent bacterial growth. The residual amount after production is also useful to prevent bacterial growth while the vaccine is stored.
  • Egg protein which is present in influenza and yellow fever vaccines because chicken eggs are used in the production of theses vaccines.

Complete listings of vaccine components specific to each vaccine are available at: Institute of Vaccine Safety, Johns Hopkins UniversityGoes to JHU Website.


  1. Offit PA, Jew RK. Addressing parents' concerns: do vaccines contain harmful preservatives, adjuvants, additives, or residuals? Pediatrics. 2003 Dec;112(6 Pt 1):1394-7 Goes to NCBI Website.
  2. CDC, Ingredients of Vaccines Fact SheetGoes to CDC Website.

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Last Updated: May 15, 2024
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