Claim that a mouse study shows COVID-19 vaccine causes “turbo cancer” distorts study findings

“New Study Links Pfizer’s COVID Vaccine to ‘Turbo Cancer’”
Fails to grasp significance of observation: The claim is based on the occurrence of cancer in one mouse out of 14. This mouse had already shown signs of illness even before receiving the vaccine, suggesting the cancer could have well been present before the vaccine was administered. No other mice in the study were found to have cancer.
Lack of context: The mice injected with COVID-19 vaccine received a dose that was several hundred times greater than that used in humans. No mention of this was made by The Florida Standard nor did it acknowledge the fact that this dose is irrelevant in the context of vaccination.
To date, more than 270 million people in the U.S. have received at least one dose of COVID-19 vaccine. Incidental cases of illnesses, including cancer, occurred even before COVID-19 vaccines existed. Therefore, in order to determine if vaccination raises the risk of illness, it isn’t enough to simply point to cases occurring after vaccination as evidence. One must compare the incidence of the illness following vaccination with the baseline incidence. There’s no evidence indicating that COVID-19 vaccines raise the risk of developing cancer or that they worsen cancer.

FULL CLAIM: “New Study Links Pfizer’s COVID Vaccine to ‘Turbo Cancer’”; “A recent scientific study published in the journal Frontiers in Oncology links the Pfizer-BioNTech COVID-19 vaccine to the development of aggressive cancer.”


On 13 July 2023, the website The Florida Standard published an article carrying the headline “New Study Links Pfizer’s COVID Vaccine to ‘Turbo Cancer’”. Screenshots of the article’s headline circulated on social media in July 2023, with some users implying that this showed COVID-19 vaccines are unsafe like in this Instagram post. The claim is based on a study published in the journal Frontiers in Oncology in May 2023.

In the study, researchers injected a group of mice with the Pfizer-BioNTech COVID-19 vaccine while the control group was injected with saline (each group had 14 mice), with the aim of studying mRNA vaccine-induced myocarditis. One mouse in the group that received the vaccine died after receiving the vaccine. The researchers reported that the mouse had died from B-cell lymphoma.

However, the study doesn’t offer sufficient evidence for the claim, and there’s no evidence establishing that COVID-19 vaccination causes cancer or worsens cancer. We explain why below.

The study’s experiments don’t accurately reflect what happens in COVID-19 vaccination

David Gorski, a surgical oncologist and professor at Wayne State University, discussed the study on his blog Respectful Insolence under his pen name Orac. He raised significant issues with the experimental protocol, one of which was the massive vaccine dose given to the mice.

The authors wrote that they administered six micrograms of vaccine diluted in 60 microliters of saline, giving approximately 0.25 micrograms of vaccine per gram of body weight.

Gorski noted that this meant the mice weighed around 24 grams at the start of the experiment. Humans typically receive 30 micrograms of vaccine (a microgram is one-millionth of a gram), five times the dose that the mice received. Assuming a “typical” human weight of 70 kilograms, the human dose would be approximately 0.000428 micrograms per gram body weight.

This means that the mice received nearly 600 times the human dose when we account for body weight, he pointed out. In short, this dose is irrelevant in the context of vaccination.

The mouse that died showed signs of illness even before receiving the vaccine

Gorski also highlighted an anomaly in the mouse’s change in weight during the study, noting that the mouse had already begun to lose weight about a week before it even received the vaccine. Weight loss in mice is commonly used to measure morbidity (a state of illness) in mouse studies.

This led him to raise the question of whether the mouse was already sick with cancer before it received the vaccine. He also found the rapidity with which the mouse died to be unusual: “In all my previous years working with mouse tumor models, I am not aware of any that go from undetectable to killing the mouse in under 16 days”.

On top of this, he also highlighted the fact that the mouse strain used in the study (BALB/c) is known for developing cancer, including lymphomas, spontaneously[1]. Therefore, the observation that one mouse out of 14 developed cancer could fall well within the baseline rate of cancer in this mouse strain.

The authors of the study also acknowledged this possibility, writing that “a causal relationship between the SARS-CoV-2 mRNA vaccine and [B-cell lymphoblastic lymphoma] observed in the present case cannot be unequivocally established and may represent coincidence”. However, they also considered that the lymphoma occurring after vaccination “suggests” the vaccine could be involved. That said, a temporal relationship alone cannot establish causality (which would be a logical fallacy known as post hoc ergo propter hoc).

No evidence that COVID-19 vaccination increases the risk of cancer

The U.S. National Cancer Institute states that “There is no evidence that COVID-19 vaccines cause cancer, lead to recurrence, or lead to disease progression”. It recommends that people with cancer and cancer survivors get the COVID-19 vaccine, as they are at a high risk for severe complications from COVID-19.

While those receiving immunosuppressive drugs, such as patients who just received a stem cell transplant, are recommended to delay COVID-19 vaccination, this is because vaccination is less effective due to the immunosuppression, not because of safety issues.

Similar claims have cited reports of cancer in vaccine adverse event report databases like the U.K.’s Yellow Card System as evidence, but this is also misleading. The Yellow Card website clarifies that “Conclusions on the safety and risks of the vaccines cannot be made on the data shown in the report alone” and that “Reporters are asked to submit Yellow Card reports even if they only have a suspicion that the vaccine may have caused the adverse reaction. The existence of an adverse reaction report does not necessarily mean that the vaccine has caused the reaction”.

Moreover, cancer was already occurring in people even before the COVID-19 vaccines existed. Given that more than 270 million people in the U.S. have since received at least one dose of vaccine, there will be cases of cancer that arise purely by chance. This was explained in a STAT News article:

Every single day, people die unexpectedly. They have strokes and heart attacks and seizures. On an average day, 110 people in this country may develop Bell’s palsy, a temporary facial paralysis, and another 274 will develop Guillain-Barré syndrome, a form of paralysis that usually resolves over time. The trigger for these medical events often isn’t known. But when they happen shortly after someone gets a vaccine — especially a new one — well, conclusions will be drawn. […]

Heart attacks occur most commonly in the morning, yet we don’t blame breakfast for causing them. A heart attack on the morning after a Covid-19 vaccine, though? That might be another matter.”

If COVID-19 vaccination did cause rapidly progressing and lethal cancer in the space of weeks at an incidence of one in 14, as some purport this mouse study to show, we would have already seen an unprecedented and sudden spike in cancer deaths in hundreds of millions of people, given that more than five billion people worldwide have received at least one dose of COVID-19 vaccine. Such a striking phenomena of widespread cancer deaths cannot have gone unnoticed, and it has clearly not occurred, thereby contradicting the claim.


In summary, claims that a mouse study by Eens et al. shows COVID-19 vaccination causes “turbo cancer” misinterpret the study’s findings and fail to understand its limitations. The Florida Standard article distorted the conclusions of the study by claiming it showed a “link to ‘turbo cancer’”, incorrectly lending readers the impression that the study was relevant to humans.

In fact, the study used a vaccine dose that was several hundreds of times greater than the human dose—in short, a dose that is irrelevant to vaccination. The mouse that died of lymphoma also showed signs of illness even before it received the vaccine dose, therefore it is doubtful that the vaccination played a role in causing the lymphoma. Taken together, the study provides no evidence supporting the alleged “link to ‘turbo cancer’”, and by claiming otherwise, the Florida Standard article misrepresented the study.

There’s currently no evidence establishing a causal relationship between cancer and COVID-19 vaccination. The U.S. National Cancer Institute recommends that people with cancer and cancer survivors get the COVID-19 vaccine, as they are at a higher risk of complications from the disease.



Published on: 20 Jul 2023 | Editor:

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