Do the COVID vaccines cause turbo cancer?
Coming to an ACIP meeting near you
Observational medical studies have numerous well-known problems. Observational studies of vaccines, in particular, suffer from fundamental limitations. The vaccine skeptics who now run the CDC’s Advisory Committee on Immunization Practices recently pointed out one particular limitation that has systematically overestimated the effectiveness of COVID shots: the healthy vaccinee effect. That is, people who receive a vaccine tend to be healthier and have better access to care than people who do not receive a vaccine. This is one reason why I’ve been advocating for new randomized trials of the COVID vaccines since 2022. RCTs avoid these confounding influences.
Yesterday, a new analysis of one potential harm of the COVID shots was published. This brief observational cohort study out of South Korea assessed whether COVID vaccines might be linked to a higher incidence of cancer.
The hypothesis that there is a vaccine-cancer connection has been circulating in anti-vaccine communities for a long time. A few months ago, I wrote about how Joe Biden’s prostate cancer diagnosis led to accusations that immunizations had caused him to develop a “turbo cancer.” I expect this new study will soon be touted by the administration to sow further doubts about vaccines and pursue policies to limit access to them.
The analysis, which used insurance claims data, found that the overall incidence of all cancers was increased in vaccine recipients. The key figure from the paper is shown below.
This superficially alarming finding should be viewed as skeptically as similarly constructed studies purporting to prove the safety and efficacy of the COVID vaccines (or even the long-term harms of the SARS-CoV-2 virus). An old CDC study, for instance, used a lower non-COVID death rate among vaccinees as evidence that immunizations don’t cause unexpected deaths. This was silly when the CDC did it then, and it’s silly now.
In the new study on COVID vaccines and cancer, notice how the incidence curves separate almost instantaneously. (The index date was set as the day after vaccine completion). Just one month after vaccination, the cancer incidence rate was already significantly higher (2.91 vs. 1.63 per 100k) in vaccinated individuals! This is almost certainly not a causal effect. No carcinogen can induce cancer that quickly. Mutations take time to accumulate and cells take time to replicate. Furthermore, the outcome measured is not the development of cancer but the diagnosis of cancer. Once a cancer develops in the body, it still takes time for it to come to the attention of the patient and healthcare system. How could anything possibly cause a cancer to not only grow but grow large enough to be detected in a matter of days?
To quote oncologist Vinay Prasad—Robert F. Kennedy Jr’s hand-chosen vaccine chief at FDA—“It is biologically inconceivable for such an effect to take place. Instead, the results suggest residual confounding.” This quote comes from a 2023 perspective in which he warned against relying on observational studies where the event curves separate almost immediately.
There are many potential confounders at play in this case, but healthy vaccinee bias could certainly be one possibility. The Korean study attempted to control for population differences between the vaccinated and unvaccinated groups using propensity scores, which are a standard but imperfect solution. We should still expect underlying differences between those who choose to be vaccinated and those who don’t to affect the results.
On the surface, a higher cancer rate in the vaccinated group would not seem to follow the idea of a “healthy vaccinee.” Aren’t they sicker in this case? But take a look at which cancers (in red) showed a significant increase in incidence: thyroid, lung, colon, stomach, breast, and prostate.
All of these cancers are ones for which the healthcare system screens asymptomatic patients. This has two major implications. First, the cancers we screen for tend to be among the slowest growing, which is why we have time to catch them with testing that only takes places every year or few years. These are the cancers least likely to be affected by a short term risk factor. Second, access to and tendency to attend cancer screening is itself a sign of health and wealth. Studies have shown that patients who undergo cancer screening live longer than those who don’t—not because of screening but from the fact that these people are better off in various other ways.
We can also look at some related data to see if this result makes any sense. If COVID vaccines could cause a detectable cancer to form in a matter of days or weeks, then surely it would also lead to an increase in deaths within a few years. Yet age-adjusted cancer death rates in the US have been relatively flat in the years since the shots came out and the vast majority of the population received them.
I suppose there is no reason to say that we definitively know the COVID vaccines don’t lead to any increased risk in any cancer over any period of time. It’s nearly impossible to prove a negative. I’d be happy to look at more data on the subject. But this study ain’t gonna do it for me.
Still, expect RFK Jr, ACIP, and vaccine skeptics in general to jump on this result to support the conspiracies they believe about “turbo cancer.” This study was already shared on social media by a member of ACIP’s COVID vaccine workgroup. In the current era, critical review of scientific data only applies to the conclusions with which you disagree.
UPDATE (9/29/25): Here is Korean cancer incidence data until 2022 showing absolutely no increase at the population level for the very cancers purportedly affected by the vaccines. Since the population was widely immunized by this point and the effect supposedly occurs near-instantly, this real-world data is highly contradictory.
You made a valid point but it rests on the genetic hypothesis of cancer origin: "This is almost certainly not a causal effect. No carcinogen can induce cancer that quickly. Mutations take time to accumulate and cells take time to replicate."
This hypothesis has been challenged by the nuclear cloning of embryonal carcinoma cells, yielding normally developing mice, cancer-free mice: https://pmc.ncbi.nlm.nih.gov/articles/PMC521109/pdf/10113985.pdf
This, despite the tumorigenicity of EC cells when directly injected in adult mice, suggesting cancer has a strong epigenetic dimension, not to mention the Warburg hypothesis and the role of the immune system in maintaining cancerous cells under control.
I find the fact that the two types of vaccine considered, adenovirus vs. mRNA have distinct but partly overlapping patterns of the type of cancers they would stimulate, an argument for some level of causal relationship. Indeed, in the case of mRNA vaccine, the mRNA is modified, and the effect of that modification is striking in a murine melanoma model: https://pmc.ncbi.nlm.nih.gov/articles/PMC9614103/pdf/fimmu-13-983000.pdf Unmodified mRNA reduces tumor growth, whereas modified mRNA stimulates tumor growth and metastasis to the lungs. And it is rapid, two weeks after the second injection and the lungs are chock-full of metastases. What do you say?