The question about polio vaccine causing cancer mainly raise from two incidents. In 1955, in the early years of polio vaccination, lots of the vaccine produced by one company actually contained live poliovirus, which caused 250 cases of the disease polio and 10 deaths. The second incident occurred in 1960 when scientists discovered that some of the monkey kidney cells used to make the polio vaccines were contaminated with simian virus 40. This virus is harmless for monkeys. But in high doses, SV40 can cause cancer in lab rats. Thus, in 1961, authorities required new lots of polio vaccines to be free of SV40.
Professor emeritus of molecular microbiology and immunology at Johns Hopkins University, Keerti Shah, showed in a research published in International Journal of Cancer that not all of the vaccines given to people during this period were contaminated with SV40. The contaminated vaccines also had formalin as a component which kill the poliovirus and SV40 in the vaccine.
National Academies’ Institute of Medicine (now the National Academy of Medicine) reviewed in 2002 saying that the available research on the subject and found “that the evidence was inadequate to conclude whether or not the contaminated polio vaccine caused cancer.”
Studies showed that people who received the polio vaccine in the 1950s and 1960s had no increased risk of cancer, but these studies had “substantial limitations,” the National Academy of Medicine said, the limitations were that, these studies were “ecologic,” the report explained. Ecologic studies look at groups — in this case, people who received the polio vaccine in the 1950s and 1960s — not individuals.
Shah said in his 2006 research published in International Journal of Cancer that “these data by themselves do not disprove the role of SV40 in human cancer because the exposure to SV40 by the vaccine is not known at the level of the individual.” But given this more recent research, it’s “very likely that SV40” is “not linked to any human cancer,” he concluded.
Present day’s scientific evidence suggest that contaminated vaccine in the 1950s and 1960s doesn’t cause cancer. However, it is also impossible for scientist to rule out the possibility that it may have done so in a handful of people. Today’s polio vaccines are free of SV40, hence foes not have any possibility of causing cancer.