Two upcoming studies by scientists at the National Cancer Institute (NCI), one of the National Institutes of Health, provide further evidence that exposure to simian virus 40 (SV40) is not associated with cancer in humans. Some U.S. polio vaccines administered from 1955-1962 were accidentally contaminated with SV40 because the vaccines were grown in monkey kidney tissue. Before the discovery of the virus led to changes in vaccine manufacture, millions of Americans received SV40-contaminated polio vaccines. This has been a significant public health concern, as SV40 has been shown to cause cancer in experimental animals. However, studies in humans have not proved conclusive.
