The polio vaccine used in the late 1950s and early 1960s was contaminated with a monkey virus called simian virus 40 (SV40), present in the monkey kidney cells used to grow the vaccine. Investigators found SV40 DNA in biopsy specimens obtained from patients with mesothelioma, osteosarcoma, and non-Hodgkin’s lymphoma. Interestingly, SV40 DNA was present in the cancers of people who had received the polio vaccine that was contaminated with SV40, but it was also present in those who had not. SV40 DNA was even found in the cancers of people born after 1963, a time when the vaccine no longer contained SV40.
A study published in 2004 shed some light on this. Some of the primers that were being employed in the PCR reactions used to amplify DNA sequences of SV40 were directed at a region of the T antigen. As it turns out, these sequences are also present in common laboratory plasmids. How did they get there? They were engineered into the plasmids during the first attempts to create expression vectors for eukaryotic cells, but this happened so long ago that their presence was not well known. When alternative T-antigen primers were used, only a few cancers were positive. Moreover, this study found no evidence of T-antigen RNA transcript production and no T-antigen protein expression in the tumors. Finally, epidemiologic studies do not show an increased risk of cancers in those who received polio vaccine between 1955 and 1963.
—Marshall, Gary S. “Addressing Concerns About Vaccines.” The Vaccine Handbook: A Practical Guide for Clinicians. 3rd ed. New York: Professional Communications, Inc., 2010. 234. Print.