evidence: Polio vaccines were indeed contaminated by SV40 at a point in time, but the claim that SV40 causes cancer in humans is not supported by scientific evidence. [...] This article by Dave Mihalovic, published on Waking Times and reproduced in several other websites, has been shared more than 21,000 times and is trending on Facebook. The article claims that the Centers for Disease Control and Prevention (CDC) "admits 98 million Americans received polio vaccine in an 8-year span when it was contaminated with cancer virus". It also asserts that this information was later "quickly removed" by the CDC. [...] Overall, the claim contains a grain of truth in that polio vaccines were indeed contaminated with SV40 at a point in time and that people did receive these contaminated vaccines. But the claim that SV40 causes cancer in humans is premature – the current state of scientific evidence is not sufficient to support a causal link between SV40 and cancer. A review by Tam et al. discussed in detail the challenges involved in evaluating this link, particularly when using past epidemiological studies (such as determining exposure levels, improvements in cancer diagnosis over the past decades)[10]. Further studies will be needed to provide a definitive answer.