Early Chronology of Events Leading to SV40 Contamination of Polio Vaccines

Throughout the 1950’s Extraneous Monkey Viruses Are Found in the Monkey Kidney Cells Used to Manufacture and Test Polio Vaccines…

Year Example Citation

Dr. Herald R. Cox of Lederle Laboratories (manufacturer of the oral polio vaccine) writes that growing poliovirus in monkey kidney tissue would pose “the potential danger of picking up other contaminating viruses or other microbic agents infectious to man”.

Herald R. Cox, Viral Vaccines and Human Welfare, The Lancet July-December 1953, pp 1-5


Scientists report that they have found a number of new monkey viruses in the kidney cells of “apparently healthy monkeys”.

Robert Rustigan, et al., Infection of Monkey Kidney Tissue Cultures with Virus-Like Agents, 1955


Scientists report the discovery of eight more monkey viruses in monkey kidney cells SV1, SV2, SV4, SV5, SV6, SV11, SV12, SV15. The scientists wrote that “Numerous filterable, transferable cytopathogenic agents other than poliovirus were also encountered (in the poliovirus vaccine)…The greatest significance of these viruses has been their appearance in tissue cultures used to produce and to test poliomyelitis vaccine”.

Robert N. Hull, et al., New Viral Agents Recovered From Tissue Cultures of Monkey Kidney Cells, American Journal of Hygiene, 1956, Vol. 63, pp. 204-215


Scientists report the discovery of 20 more monkey viruses from monkey kidney cells (SV16, SV17, SV18, SV19, SV20, SV23, SV25, SV26, SV27, SV28, SV29, SV30, SV31, SV32, SV33, SV34, SV35, SV36, SV37, SV59). The scientists state, “As long as primary monkey-kidney cultures are used in the production and testing of virus vaccines the problem of simian virus contamination will remain…the possible virulence of these viruses for man remained unknown…”

Robert N. Hull, et al., New Viral Agents Recovered From Tissue Cultures of Monkey Kidney Cells, American Journal of Hygiene, 1958, Vol. 68, pp. 31-44.

Concerned Scientists Suggest Various Methods of Eliminating SV40 from Polio Vaccines. These Suggestions Are Ignored by the Government and the Vaccine Producers…

Year Example Citation

Drs. Sweet and Hilleman publish their findings on SV40. They state that they recovered the virus from normal rhesus monkey kidney cell cultures, that SV40 may be hidden by foamy virus, that SV40 did not readily show itself in these cultures, and that other viruses could interfere with the detection of SV40. The scientists conclude that the solution to this problem is to eliminate the agent from the seed stocks and to discard any contaminated lots.

B.H. Sweet and M. R. Hilleman, The Vacuolating Virus, SV40, Proceedings of the Society for Experimental Biology and Medicine, Oct.-Dec. 1960, vol 105, pp. 420-427


Dr. Bernice Eddy of the Division of Biologics Standards of the National Institute of Health (NIH) describes her experiments that began in 1959 in which she discovered SV40 and found that it was carcinogenic to hamsters.

Bernice E. Eddy, Tumors Produced in Hamsters by SV40, 1962, pp. 930-935


Researchers report that current quality assurance for polio vaccine production only requires that kidney cell cultures be observed for two weeks, but that SV40 can take up to six weeks to show itself. These scientists suggest a more accurate detection system for SV40 (immunofluorescence). The federal government never requires this system and the vaccine manufacturers never voluntarily adopt it.

Harvey M. Shein and Jeana D. Levinthal, Fluorescent Antibody and Complement Fixation Tests for Detection of SV40 Virus in Cell Cultures, Virology, Vol. 17, 1962,pp. 595-597.


Researchers state that SV40 is “considered a potential hazard” and suggest that a substance (beta-propiolactone or BPL) be used to inactivate SV40. The federal government never requires this system and the vaccine manufacturers never voluntarily adopt it.

Hajime Hayashi and Gerald LoGrippo, Inactivation of Vacuolating Virus (SV40) by Beta-Propiolactone, Henry Ford Hospital Bulletin, Vol. 10, 1962, pp. 463-470.


Researchers at Harvard report that SV40 is not only carcinogenic to hamsters but also transforms (causes to be cancerous) human kidney cells in culture.

Hajime Hayashi and Gerald LoGrippo, Inactivation of Vacuolating Virus (SV40) by Beta-Propiolactone, Henry Ford Hospital Bulletin, Vol. 10, 1962, pp. 463-470.


Renowned virologist Joseph Melnick discusses the problems with the SV40 test used by the vaccine manufacturers (cultures often develop nonspecific degeneration which complicates the results).

He also describes a more precise system to detect SV40. “A plaque assay has been developed to fill the need for a more precise virus assay and a more sensitive antibody detection system…The availability of a precise virus assay procedure is of more than academic interest in view of the frequent detection of this virus in vaccines designed for human use…” The vaccine manufacturers never adopted the assay system.

This paper also states that “the strain of (SV40) virus used (in these experiments) was one isolated from Sabin’s lot of type 2 oral poliomyelitis vaccine…”

Melnick JL, Stinebsugh S Plaque Formation by Vacuolating Virus, SV40 Virology, Vol 1, No. 3, 1962, pp. 348-350.

Joseph Melnick was the Virus Laboratories Chief of the NIH’s Biologics Standards Division, before he became dean of the Biomedical Sciences Graduate School at Baylor University


This 1962 paper came from the Division of Biological Standards of the NIH. Incredibly, the authors state that five weeks is necessary to consistently detect SV40 in monkey kidney cell cultures. (Two weeks was all the law required.) The paper also states that low concentrations of SV40 will not be detectable with the methods used by the vaccine producers. The paper stated, “It is desirable to hold Cercopithecus cell cultures…for periods longer than 2 weeks…since positive results were more evident in the third to fifth week than in the second.”

The authors conclude with suggesting alternative technologies to detect SV40, including complement fixing and photodynamic inactivation. The vaccine manufacturers never adopted any of these methods.

The authors also state, “It is our opinion that the most expeditious approach to the elimination of infectious SV40 from viral vaccines prepared from monkey kidney cultures is to avoid the use of animals which may have been exposed to the agent.”

Meyer HM, Hopps HE, Rogers NG, Brooks BE, Bernehim BC, Jones WP, Nisalak A, Douglas RD (1962) Studies on Simian Virus 40. Journal of Immunology Vol 88:796-805.


This article co-written by Ruth L. Kirschstein, (now the Deputy Director of the NIH), describes how SV40 can cause brain tumors in hamsters. (The tumor she specifically addresses is ependymoma which is a pediatric brain tumor that has since been found to contain SV40.)

Kirschstein RL, Gerber P (1962) Ependymomas produced after intracerebral inoculation of SV40 into new-born hamsters, Nature Vol 195:299-300.


Scientists were aware that OPV manufacturers had not changed their method for detecting SV40. By 1965 these concerns became more explicit in the medical literature.

For example, this 1965 study reported that low doses of SV40 would not cause a CPE but only some intranuclear inclusions. This study was supported in part by a U.S. Public Health Service Career Development Award and the NCI. It concluded with: “Finally the demonstration that SV40 can multiply in cultures derived from African Green Monkey Kidney Cells without exhibiting any cytopathic effect detectable under non-stained, direct light microscope observations suggests that as far as this agent is concerned more attention should be given to the present safety tests used concerning vaccines prepared in monkey cells.”

More attention was not given.

Mario V. Fernandes, Paul S. Moorhead of the Wistar Institute, Transformation of African Green Monkey Kidney Cultures Infected with Simian Vacuolating Virus SV40, Texas Reports on Biology and Medicine, Volume 23, p 242 at 256-257 (June 1965).

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