How OPV was Produced
Once their polio seeds were isolated, pharmaceutical companies needed a method to propagate the viruses in order to produce the vast quantities of vaccine needed for nation-wide immunization campaigns. This required a medium or substrate upon which the poliovirus could be efficiently grown and harvested. Kidney cells from rhesus monkeys were chosen because they were found to be an effective growth medium. A small quantity of poliovirus could be added to the minced kidneys surgically removed from these monkeys and within a few days, large quantities of poliovirus could then be harvested from these same monkey cells.
There was a problem, however, with using these monkey kidney cells to both create the original vaccine strains and grow the vaccine in large quantities. Monkeys contain simian viruses. And the monkeys they used (i.e. rhesus and African Greens) are known carriers of SV40. When the poliovirus was passaged through these monkeys or grown on the monkey kidney cells for production, extraneous viruses became part of the final poliovirus vaccine. As early as 1953, Dr. Herald R. Cox, a scientist working at Lederle Laboratories, one of the polio vaccine manufacturers, published an article in a peer reviewed scientific journal in which he stated:
“[P]oliomyelitis virus has so far been cultivated only in the tissues of certain susceptible speciesnamely, monkey or human tissues. Here again we would always be confronted with the potential danger of picking up other contaminating viruses or other microbic agents infectious for man.”
In fact, in 1958, a scientific journal reported that “the rate of isolation of new simian viruses (from monkey kidney cells) has continued unabated.” Additionally, in 1960, the pharmaceutical company Merck & Co. wrote to the U.S. Surgeon General:
“Our scientific staff have emphasized to us that there are a number of serious scientific and technical problems that must be solved before we could engage in large-scale production of live poliovirus vaccine. Most important among these is the problem of extraneous contaminating simian viruses that may be extremely difficult to eliminate and which may be difficult if not impossible to detect at the present stage of the technology.”
 M.R. Hilleman, Discovery of Simian Virus (SV40) and its Relationship to Poliomyelitis Virus Vaccines, in Simian Virus 40 (SV40): A Possible Human Polyomavirus, 94 Dev. Biol. Stand. 18390 (F. Brown & A.M. Lewis eds., 1998).
 Id. at 184.
 Herald R. Cox, Viral Vaccines and Human Welfare, The Lancet, July 4, 1953, at 1, 3.
 Robert N. Hull et al., New Viral Agents Recovered from Tissue Cultures of Monkey Kidney Cells, 68 Am. J. Hygiene 31, 41 (1958).
 Kops, supra note 15, at 4745, 4747.