Vaccines may contain "live viruses, killed viruses, purified viral proteins, inactivated bacterial toxins or bacterial polysaccharides," which is how our bodies know how to develop antibodies and an immune response against the infection that the vaccine is supposed to protect us against.
Vaccines also contain additives and preservatives.
The most well-known preservative in vaccines is thimerosal, which was once thought to possibly be linked to autism.
Although no link to autism or other conditions was ever found, because of concerns that thimerosal could be harmful and because alternatives to thimerosal are now available, according to the FDA, "thimerosal has been removed from or reduced to trace amounts in all vaccines routinely recommended for children 6 years of age and younger, with the exception of the inactivated influenza vaccine."
Still, some parents are worried that chemicals, additives and preservatives in vaccines are harmful, which has prompted the Green Vaccine initiative to call for safer vaccines.
Vaccine Additives and Preservatives
Although mercury has been removed from most vaccines, vaccines may still contain aluminum, formaldehyde, human serum albumin, gelatin, antibiotics and yeast proteins.
Why?
Some, such as aluminum salts, help the vaccine to work better. Other additives, such as human serum albumin, help stabilize live viruses in the vaccine. And others, such as formaldehyde, antibiotics, egg proteins and yeast proteins, are left over in residual amounts from the way that vaccines are made.
Formaldehyde? Why is formaldehyde in the vaccines that we give our children?
Formaldehyde is present in some of the vaccines on the childhood immunization schedule, including the flu shot, polio vaccine and DTaP vaccine, because it works to eliminate the harmful effects of these bacterial toxins and makes the viruses unable to replicate or reproduce themselves. The very small amount of formaldehyde that is left over in the vaccines that are given to kids is less than the amount naturally found in children and much less than that amount safely given to animals in research studies.
What about antifreeze? Don't vaccines have antifreeze in them?
Not really. Some vaccines do contain the additive 2-phenoxyethanol, which is an organic chemical compound, but it is not the same as antifreeze (ethylene glycol and propylene glycol). 2-Phenoxyethanol is also a glycol ether and doesn't sound much better than antifreeze, so why is it in vaccines? It is a preservative that can help prevent bacterial and fungal contamination of the vaccine.
Safety of Vaccine Additives and Preservatives
Unfortunately, vaccine additives do sometimes cause reactions, with the most common being allergic reactions to gelatin, the antibiotic neomycin and eggs (flu shot and yellow fever vaccine).
Still, these reactions are very rare.
According to the AAP, "Parents should be reassured that quantities of mercury, aluminum and formaldehyde contained in vaccines are likely to be harmless on the basis of exposure studies in humans or experimental studies in animals."
And keep in mind that it was much more common for children to get sick from contaminated vaccines before the use of preservatives. Also, of course additives that have helped vaccines work better have helped prevent millions of vaccine preventable illnesses and deaths.
Sources:
Addressing Parents' Concerns: Do Vaccines Contain Harmful Preservatives, Adjuvants, Additives, or Residuals? Paul A. Offit, MD. PEDIATRICS Vol. 112 No. 6 December 2003, pp. 1394-1397
Centers for Disease Control and Prevention. Ingredients of Vaccines - Fact Sheet
Plotkin: Vaccines, 5th ed.
