Glyphosate, often sold under the brand name “Roundup,” is the most widely used weed killer in the U.S. Glyphosate is a “non-selective herbicide,” which means it kills many plants, not just weeds. It kills them by interfering with the production of critical proteins necessary for growth.

In commercial agriculture, Roundup is used on “Roundup Ready” crops—crops that have been genetically modified to resist the powerful toxic effects of glyphosate. The list of Roundup Ready crops includes soy, corn, canola and sugar beets. It is important to remember that, while these plants have been modified to resist the harmful effects of glyphosate, the people and animals that eat them have not.

In a series of articles, my colleague Anthony Samsel and I have been exploring the connection between glyphosate and a number of diseases, including multiple sclerosis, autism, Alzheimer’s disease, and cancer. In our most recent article, “Glyphosate Pathways to Modern Diseases VI: Prions, Amyloidoses and Autoimmune Neurological Diseases,” we present evidence that glyphosate has made its way into several widely used vaccines. We describe how the glyphosate residue contained in vaccines might induce the kind of autoimmune responses typically observed in autism.

Interestingly, of all the vaccines we tested, MMR stood out as consistently having the highest level of glyphosate contamination. This fact may help explain why the MMR vaccine, which contains neither mercury nor aluminum, has been implicated so often in vaccine injury and autism.

How Might Glyphosate Make Its Way into Vaccines?

Vaccines can become contaminated in many ways. One potential source of contamination is the animal tissue (chicken embryo, fetal bovine serum, monkey kidney, etc.) that is used as a culture medium to grow the viruses contained in vaccines. The measles virus for the MMR is grown on gelatin made from the bones and ligaments of commercially raised cows and pigs, animals that have been fed a steady diet of Roundup Ready corn and soy feed. Gelatin is also used as a stabilizer in vaccines, creating another possible route of contamination.