During the polio panic of the 1950s, the Salk vaccine was developed and rushed into production without proper testing. The polio vaccine was cultured on the kidneys of monkeys. Unfortunately, what were then unnoticed, or thought to be harmless monkey viruses, contaminated the vaccines that were given to more than 200 million Americans. The follow-on testing by our National Institutes of health demonstrated that these “monkey viruses” were strongly carcinogenic. They caused "galloping" cancers in all animal subjects tested, even humans.