Polio vaccines used in the late 1950s and early 1960s were contaminated with a virus called simian virus 40 (SV40) present in monkey kidney cells used to grow the vaccine. Subsequently, investigators found SV40 DNA in biopsy specimens obtained from patients with cancers, such as mesothelioma (lung), osteosarcoma (bone) and non-Hodgkins lymphoma (lymph nodes). However, several facts should be noted:

1. SV40 was present in cancers of people who either had or had not received the polio vaccines that were contaminated with SV40.
2. SV40 has not been present in any vaccine since 1963. 
3. People with cancers who were born after 1963, when SV40 was no longer a contaminant of the polio vaccine, were found to have evidence for SV40 in their cancerous cells. 
4. Epidemiologic studies do not show an increased risk of cancers in those who received polio vaccine between 1955 and 1963.

Taken together, these findings do not support the hypothesis that SV40 virus contained in polio vaccines administered before 1963 caused cancers. 

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