Simian virus 40 (SV40) is a monkey poliomavirus that was a contaminant of vaccines produced in the 1950s and early 1960s, including the inactivated polio vaccine, which was given to millions of people. SV40 causes cancer in laboratory animals, and more controversially, SV40 DNA has been detected in some human tumors. Nonetheless, it is not known whether SV40 causes human cancer. These studies look at the association between SV40 and human cancer.
