As I recall, SV40 stands for “Simeon Virus 40” and it was accidently included in the polio virus that was given to 120 million people in the 1950’s.
“Cancer risk associated with simian virus 40 contaminated polio vaccine”
https://pubmed.ncbi.nlm.nih.gov/10472327/
Abstract
“The presence of SV40 in monkey cell cultures used in the preparation of the polio vaccine from 1955 through 1961 is well documented. Investigations have consistently demonstrated the oncogenic behavior of SV40 in animal models.”
“Recently, investigators have provided persuasive evidence that SV40 is present in human ependymomas, choroid plexus tumors, bone tumors, and mesotheliomas, however, the etiologic role of the virus in tumorigenesis has not been established.”
Conclusions: These data suggest that there may be an increased incidence of certain cancers among the 98 million persons exposed to contaminated polio vaccine in the U.S.; further investigations are clearly justified.
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On a separate note:
The Cutter Incident was a 1955 polio vaccine scandal in which some batches of the vaccine contained live polio virus. The incident led to the creation of a stronger system for regulating vaccines.
The Cutter Incident: How America’s First Polio Vaccine Led to a Growing Vaccine Crisis
The Cutter polio vaccine was contaminated with simian virus 40 (SV40) in the 1950s and 1960s. The contamination was due to the use of monkey kidney cells in the vaccine production process.