Not Real News

On Friday, The Associated Press reported on stories circulating online incorrectly claiming the Centers for Disease Control and Prevention admitted that 98 million Americans were given a “cancer virus” through the polio vaccine. 

CLAIM: The Centers for Disease Control and Prevention admitted that 98 million Americans were given a “cancer virus” through the polio vaccine.

THE FACTS: The CDC has made no such statement, and the claim misrepresents a fact sheet put out by the agency more than 10 years ago about some polio vaccines that were administered between 1955 to 1963. The agency has said that that 10-30 percent of the 98 million shots administered in that period were contaminated with simian virus 40, or SV40, but that most studies have found no causal relationship between SV40 and cancer in humans.

An Instagram user posted a screenshot of an article making the erroneous claim, with a headline reading: “CDC admits 98 million Americans were given cancer virus via the polio shot.” The headline comes from a 2015 article published by, which is part of Natural News Network, a massive collection of sites known for anti-vaccine content and health misinformation.

Natural News Network did not respond to a request for comment. But the headline misrepresents a document put out by the CDC about a real episode in the 1950s and ’60s, when some polio vaccines were contaminated with SV40, which came from monkey kidney cells used to make the shots at the time. The article cites a fact sheet on the incident that was dated from 2007, and was removed from the CDC’s website in 2013, according to archives of the page on the Wayback Machine. The document says more than 98 million people in the U.S. were vaccinated against polio between 1955 to 1963, and SV40 had contaminated 10-30 percent of those immunizations.

“SV40 virus has been found in certain types of cancer in humans, but it has not been determined that SV40 causes these cancers,” reads the old fact sheet. The CDC confirmed in a statement to the AP that the claim spreading online about the polio vaccine is false. A new page on the agency’s website that discusses the incident says that there had been concern about SV40’s effects on humans because it had been found to cause cancer in laboratory animals.

“However, most studies looking at the relationship between SV40 and cancers are reassuring, finding no causal association between receipt of SV40-contaminated polio vaccine and development of cancer,” the page now reads. The page says “most” because a series of studies published starting in 1994 did link SV40 to cancer in humans.

But Dr. Paul Offit, an expert in virology and immunology who is the director of the Children’s Hospital of Philadelphia Vaccine Education Center, said those findings could not be replicated by others. The “enormous amount of epidemiological evidence” shows that people who received polio vaccines containing SV40 do not have an increased risk of cancer, Offit told the AP. “In short, SV40 virus, which was a contaminant in those early vaccines, and could cause cancer in experimental animals, did not cause cancer in people,” he said.

— Associated Press writer Melissa Goldin in New York contributed this report.