Vaccines contain either killed or weakened forms of disease-causing bacteria or viruses, or components of these that stimulate a response by the body’s immune system, which then protects against the development of disease.

Although synthetic media have been developed for growth of many medically important microorganisms, some still require additional nutrients which are provided by animal-derived products such as serum and blood. No bovine material has ever been used as an active ingredient of any vaccine.

In the late 19th century, microbiologist began to grow bacteria in the laboratory. The early bacteriologist tried to mimic as closely as possible the infected person’s tissues by using sugars, salts, and various meat extracts to make “growth media.”

These kinds of conditions were quite successful in growing bacteria and then viruses in the lab, because these media supplied the many necessary nutrients.