The amount of formaldehyde present in some infant vaccines is so small compared to the concentration that occurs naturally in the body that it does not pose a safety concern, according to a study using a mathematical model developed by scientists at the U.S. Food and Drug Administration (FDA).
Formaldehyde has a long history of safe use in the manufacture of certain viral and bacterial vaccines. It is used to inactivate viruses so that they don’t cause disease (e.g., polio virus used to make polio vaccine) and to detoxify bacterial toxins (e.g., the toxin used to make diphtheria vaccine). Formaldehyde is diluted during the vaccine manufacturing process, but residual quantities of formaldehyde may be found in some current vaccines.
Formaldehyde is also produced naturally in the human body. It is essential for the production of some basic biological materials, such as certain amino acids. Amino acids are necessary for important life processes as they are the building blocks of proteins in the body.
Formaldehyde is also found in the environment. For example, it is used in the manufacture of building materials, as a preservative for specimens in labs and to make many household products.
The latest research has shown that the highest risk of harmful effects from formaldehyde is from breathing it, and this occurs more frequently in people who routinely use formaldehyde in their jobs.
Exposure to formaldehyde from vaccines differs from environmental exposure because the small amount of formaldehyde via injection with a vaccine occurs briefly and only occasionally.
When the body breaks down formaldehyde it does not distinguish between formaldehyde from vaccines and that which is naturally produced or environmental.
Using modeling, the FDA scientists assessed the concentrations of formaldehyde in the blood and total body water of a hypothetical 2-month-old infant following injection of formaldehyde containing vaccines into the muscle at a single medical visit.
They compared this estimate with the natural levels of formaldehyde that occur in the body. The model considered the natural reactions in the body that process formaldehyde and how long it would take for these processes to occur.
To ensure that the model did not underestimate the amount of formaldehyde the infant was exposed to, the FDA scientists assumed that the hypothetical 2-month old infant was in the 10th percentile for age-weight relationship for the United States. Such an infant would receive the highest maximum exposure to vaccine formaldehyde relative to its weight.
Based on a maximal level of 200 micrograms of formaldehyde exposure from vaccination, the FDA model showed that the majority of the formaldehyde is essentially completely removed from the injection site within 30 minutes. The majority of the formaldehyde is broken down (metabolized) in the muscle and any remaining formaldehyde enters the bloodstream and body water. The model showed that at its highest concentration this remaining formaldehyde is less than 1% of the existing, naturally occurring level of formaldehyde in the body. The FDA scientists note that the natural level of formaldehyde in the body is more than 100 times higher than that found in vaccines. Moreover, there are no known adverse health affects from this naturally occurring formaldehyde. They concluded that the temporary presence of a very small amount of additional formaldehyde contributed by vaccination would pose no safety concerns.
This study is part of a rigorous and ongoing evaluation of the safety of biological products for which FDA has oversight.
“Pharmacokinetic modeling as an approach to assessing the safety of residual formaldehyde in infant vaccines”
Article in Press Vaccine (2013)
Robert J. Mitkusa, Maureen A. Hessb, and Sorell L. Schwartza,c
aOffice of Biostatistics and Epidemiology U.S. FDA Center for Biologics Evaluation and Research, Rockville, MD 20852
bOffice of Vaccines Research and Review, U.S. FDA Center for Biologics Evaluation and Research, Rockville, MD 20852
cDepartment of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, 20057