Most people, including many doctors, think that vaccines are free of contaminants. But nothing could be further from the truth. In fact, virtually all vaccines contain some sort of contaminant.

According to microbiologist Maurice Hilleman, the older vaccines were contaminated with numerous viruses and bacteria, many known to cause cancer. While they are not so obviously contaminated today, careful studies still demonstrate that most have bacterial, mycoplasmal, and viral substances, including viral proteins, RNA, DNA, and other cellular fragments — all of which can trigger disease processes.

Many vaccines use bovine proteins as a culture medium to grow viruses for vaccine manufacture. A large percentage of vaccines that use these proteins are contaminated with bovine diarrhea virus, which is known to cause serious pulmonary damage in experimental animals.

One study of children under age 2 with gastroenteritis found that 30 of 128 showed evidence that the cause of the condition was a pestivirus infection.

Pestiviruses have also been linked to microcephaly, a condition in which the brain fails to fully develop.

One danger of using contaminated vaccines is that the viruses can interact with cells and other viruses in the body to generate completely new retroviruses — some of which can cause cancer.

Other bovine viruses known to contaminate vaccines include:

• Polyomavirus

• Parvoviruses

• Bovine leukemia virus

• Bovine visna virus

• Bovine immunodeficiency virus

• Mycoplasma-like organisms

Virus-like particles (68 percent) and mycoplasma-resembling microorganisms (20 percent) have been detected in samples of calf serum used in vaccine manufacturing.

Another troubling virus found in calf serum is bovine herpesvirus-4 (BHV-4), which can replicate in human cells.

These viruses can then contaminate human embryonic cell lines (WI-38 and MRC-5), which are the most common human cell lines used in vaccine manufacturing. These cell lines are used to manufacture rubella, chickenpox, and smallpox vaccines. The use of chickens and eggs also poses a hazard for potential vaccine contamination. Studies have shown that a common contaminant is the avian leukosis (leukemia) virus.