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Home » Anti-vaccine trope that polio vaccine caused cancer — debunked

Anti-vaccine trope that polio vaccine caused cancer — debunked

The old “polio vaccine caused X million cases of cancer” trope has reappeared on social media, mostly from Steve Kirsch, the ill-informed anti-vaccine activist. However, given that every anti-vaccine trope, even after being thoroughly debunked, will return as the newest and most favorite anti-vaccine claim, just like a zombie.

Although I have debunked this before, it’s important to bring back the debunking article so that when someone searches for “polio vaccine and cancer,” they will find this article before Google or Bing (yes, I use Bing) offer up anti-vaccine articles that are scientifically and logically deficient.

This article will review the anti-vaccine claims about the polio vaccine and provide the science that shows that the polio vaccine is not linked to any cancer.

Polio vaccine cause cancer – the myth

According to the anti-vaccine disinformation, the myth about the polio vaccine and cancer started when the CDC supposedly admitted that 98 million Americans received the polio vaccine during an 8-year span when it was contaminated with a cancer virus. Other websites essentially repeated the same nonsense. And it’s in the lyrics of a rap song (seriously, the stuff people send me continues to amaze me).

The first article I linked above is authored by Dave Mihalovic, who is a naturopathic doctor (typically someone who eschews science-based medicine in favor of pseudosciences like homeopathy and acupuncture). He also claims to be a “vaccine researcher.”

If Mihalovic were a vaccine researcher, wouldn’t he have a robust list of peer-reviewed articles with his name attached? Well, he has published exactly zero PubMed-indexed articles about vaccines. He actually hasn’t published anything about any medical science anywhere. His claim to being a vaccine researcher rings rather hollow.

What Mihalovic probably means is his research included a few hours on Google and thinks he’s now as smart as anyone who actually has a bachelor’s and doctoral degree in immunology, virology, biochemistry, epidemiology, or some other biomedical science that matters to real vaccine research. Of course, a real “vaccine researcher” has a decade or two or three of real scientific research in a real-world class laboratory.

Mihalovic is as much a vaccine researcher as I am an Oscar-winning screenwriter. Please note that I am not a screenwriter, let alone an Oscar-winning one. However, I could say that I write screenplays. I could claim that I am Steven Spielberg’s best buddy. But it would take you about 47 nanoseconds to find that there is no evidence of my being a screenwriter. Or that I am friends with Spielberg.

Similarly, I found no evidence that Mihalovic is or was a real vaccine researcher.  Of course, Mihalovic thinks he’s as brilliant as a real scientific vaccine researcher, but he has zero credibility as one

Nevertheless, let’s get back to the logic being used by anti-vaccine groups to “prove” that the polio vaccine caused cancer:

  1. Polio vaccines were contaminated with the SV40 virus (known as Simian virus 40, a polyomavirus that is found in both monkeys and humans),
  2. SV40 causes cancer,
  3. The CDC admits that 98 million Americans are at significant risk of SV40 infection and thus cancer.

So are you now scared? If you are older than 50, according to Mihalovic and others in the anti-vaccine crowd, including one wannabe rapper, you are carrying a virus that will give you some cancer. And this anti-vaccine zombie trope keeps coming back to life, making it even scarier.

The real science of SV40 and the polio vaccine

Responding to the anti-vaccine myth that the “polio vaccine can cause cancer” takes much more time than the investment of the anti-vaccine forces. As a scientific skeptic, with, I hope, above-average critical thinking skills, I want to smash the myth into tiny little pieces.

The fact is that of the three parts of the myth mentioned in the previous section, only the first one is partially true, and the rest are complete nonsense. None are supported by real scientific or historical evidence. But like most pseudoscience, they are based on some tiny piece of science and eventually over-exaggerated with logical fallacies, misleading terminology, and outright untruths.

Jonas Salk, hero of the war against preventable diseases.
Jonas Salk, the hero of the war against preventable diseases.

Here are the evidence-based facts, using real scientific and historical information, which anyone can read themselves to get the accurate story:

  • The groundbreaking and lifesaving polio vaccines developed separately by Jonas Salk (injected, inactivated virus, vaccine) and Albert Sabin (oral, live virus, vaccine), have been used since the 1950s. Immunization against polio went back and forth between the two versions of the vaccine, although since the early 1980s, the USA has used the Salk version of the vaccine almost exclusively.
  • The vaccines were developed in the early 1950s and were produced using VERO green monkey kidney cell lines. Typically, viruses used in vaccines need to be “grown” in a cell line, because viruses cannot replicate themselves without hijacking a normal cell, and reproduce using that cell’s machinery. I know that the anti-vaccine crowd thinks that viruses are grown magically, and you can just grab a handful of them, throw them in a blender with a dash of mercury, aborted babies, and aluminum – voila, you have a vaccine. Sorry, it’s not that easy.
  • In 1959, microbiologist Maurice Hilleman found a monkey virus in both vaccines — it was the 40th simian virus (SV) to be discovered by scientists, so it was given the moniker of SV40 (creativity in naming viruses isn’t important even today). Back in the 1950s, we didn’t have the technology that we do now to screen for contaminants in the growth medium, so the SV40 virus had contaminated the VERO line well before the beginning of production of vaccines. Not all of the VERO cells were contaminated with SV40, although the exact proportion is unknown.
  • Salk’s inactivated virus vaccine, which was treated with formaldehyde (only a tiny amount remains in the vaccine, and let’s not spend time arguing about the “danger” of formaldehyde in vaccines), had very small amounts or possibly none of the SV40 virus. On the other hand, Sabin’s live oral vaccine was heavily contaminated with SV40, because there was no treatment was performed on the vaccine to inactivate the polio virus.
  • Worried about the potential effects the virus could have on humans, researchers injected it into hamsters, finding that nearly all of them developed massive cancerous tumors. But, as I’ve said on numerous occasions, primary research should be examined carefully before accepting that it has any type of applicability to human health. And causing cancer in rodents does not necessarily have clinical significance for humans.
  • Upon further review of the initial studies, it was observed hamsters that ingested SV40, instead of being injected with it, didn’t develop any cancers. In other words, Sabin’s live oral vaccine could not cause any cancer. Additional studies showed that children who were given Sabin’s oral vaccine did not develop antibodies to SV40 – apparently, the virus quickly and safely passed through the child’s digestive system, never causing an SV40 infection.
  • On the other hand, Salk’s vaccine, which contained very little or no SV40, but was given by injection, there was evidence that some of these children might have been infected with SV40.
  • Furthermore, recent studies have shown no credible evidence (here, here, here, and here) that those children who received SV40-contaminated vaccines had an increased incidence of cancer versus unvaccinated children. No plausible evidence suggests that SV40, with or without the polio vaccine, can cause cancer in humans (pdf). A meta-review of published research from the 1960s to 2004 showed no evidence that supported any causal link between SV40 and any cancer. A review of cancers thought to be most associated with SV40 found no evidence to support causality between the virus and cancer. So even if SV40 entered into the bodies of individuals who received the polio vaccine, there is little evidence that it can cause any cancer.
  • Finally, polio vaccines have been SV40-free since 1963 in most advanced countries, although Soviet bloc vaccines were contaminated until the 1980s.


I don’t know how many bullet points I need to make, but unless someone wants to deny history, basic science, and mountains of data accumulated over the past few decades, one simply cannot make a valid claim that the polio vaccine has currently or has ever caused a single case of “cancer.” I will admit that it is biologically plausible that SV40-contaminated polio vaccines could cause cancer – however, subsequent research and the vast wealth of evidence state that it is unlikely, if not impossible, that there was any link.

Predictably, the information spread by the “polio causes cancer” articles pushed by the anti-vaccine activists is wrong on so many levels. We know that not all polio vaccines were contaminated. We know the SV40 virus in the oral vaccine merely passed through the digestive tract without infecting any cells (the first step for SV40 to actually cause cancer). We also know, as established by numerous peer-reviewed articles, that SV40 probably does not cause any kind of cancer in humans.

Even if a tiny percentage of individuals contract SV40 that leads to cancer, it’s at such a low rate that it would be impossible to detect unless we check tens of millions of patients.

Lastly, and most importantly, the claim that “98 million” might catch cancer from the polio vaccine sounds like an incredibly scary story. The number is ultimately inaccurate, a tactic employed by the anti-vaccine religion whenever it suits their needs to establish the dangers of vaccines. In other words, facts are damned, let’s say whatever sounds truly spine-chilling.

The real scientific facts are before the SV40 virus was removed from the vaccine, around 98 million children got one of the two forms of the polio vaccine. However, eliminating those who got the oral vaccine, which, as we have established, did not infect children with the SV40 virus, approximately 10-30 million Americans were immunized with the Salk vaccine that probably didn’t contain the  SV40 virus. Finally, even if all of these children were infected with SV40, there is little evidence that establishes causality for cancer.



Michael Simpson

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