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Additives in vaccines

Do vaccines contain harmful additives?

No. Some vaccines contain…


Formaldehyde may be used early in the manufacturing process to inactivate some viruses and toxins. Purification removes almost all of the formaldehyde. Formaldehyde occurs naturally in the human body and helps with metabolism. There is approximately ten times the amount of formaldehyde in a baby’s body at any time than there is in a vaccine.


Aluminum salts (aluminum hydroxide, aluminum phosphate, or potassium aluminum sulfate) are used as adjuvants, substances added to a vaccine to enhance and strengthen the immune system’s response. Adjuvants used today make it possible to reduce the amount of antigens (parts of weak or dead viruses or bacteria) in a vaccine. Monitoring of vaccines over seven decades has proven adjuvants are safe. Aluminum is the most abundant element in the earth’s crust and is found in air, food and water. Aluminum is present in breast milk and infant formula in similar amounts as in vaccines.


An ethyl mercury derivative call thimerosal is used as a preservative. No vaccine made in Canada since March 2001 for routine use in children contains thimerosal, with the exception of the influenza vaccine. DTaP, polio and Hib vaccines have not contained this preservative since 1997-98. The MMR vaccine used in Canada has never contained thimerosal.


Public Health Agency of Canada. Canadian Immunization Guide. Evergreen edition. (external link)

Canadian Paediatric Society. Your Child’s Best Shot, 4th edition (external link)

ImmunizeBC. Immunization Communication Tool for Immunizers (2008) (external link)

U.S. Centers for Disease Control and Prevention. Vaccine additives (external link)

Immunize Canada. Vaccine contents