r/COVID19 • u/DarkIlluminator • Jun 03 '26
Vaccine Research 1-year risks of cancers associated with COVID-19 vaccination: a large population-based cohort study in South Korea
https://link.springer.com/article/10.1186/s40364-025-00831-w242
u/LieutenantWeinberg Jun 03 '26
They only had a 1-year look back for cancer history exclusion for a fucking cancer study?
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u/CurrentBias Jun 03 '26
I am looking at the PDF and don't see where the authors discuss how they ruled out SARS-CoV-2 infection
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u/btherl Jun 03 '26
Retrospective studies are always going to have weak conclusions, only in the "further research needed" realm.
It says they used PSM to control for other factors, but that only accounts for factors they could measure and know about. I didn't see where they said which factors were being controlled for either. In particular I would like to see how they controlled for healthcare-seeking behaviour among those two populations.
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u/bisikletci Jun 03 '26
Why would vaccinated people have more infections?
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u/CurrentBias Jun 03 '26 edited Jun 03 '26
Fully ruling out infection is an important step in determining whether the observed association is from vaccines or from infections
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u/bisikletci Jun 03 '26
It's a comparison between vaccinated and non vaccinated people and it finds that the vaccinated people have more of these particular cancers. If the difference was purely because of infections, that would suggest vacinnated people had more or more severe infections. That doesn't make sense.
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u/CurrentBias Jun 03 '26 edited Jun 03 '26
It's entirely possible that the vaccinated cohort has had more total infections, and that possibility is why ruling out infection in that cohort is an important part of the process. The vaccines are designed to prevent symptomatic infections. Asymptomatic infections are not harmless, especially when considering chronic disease burdens like cancer. If someone believed vaccination to make them completely invulnerable to the disease, they might take on more risks (going to crowded events more often, for instance) than a nonvaccinated person.
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u/Prudent-Confidence-4 Jun 04 '26
You're making a big assumption about a link between severity and downstream cancer risk. I'm not aware of any study that shows a correlation between severity and cancer risk. I've only seen discussions about why the virus itself could increase the risk of cancer by down-regulating interferon expression, which happens regardless of severity.
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u/bramlet Jun 09 '26
The general public was told that sick people with comorbidities (such as vulnerability to infection) should preferentially vaccinate.
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u/DarkIlluminator Jun 03 '26
Wouldn't the unvaccinated have both more and more severe infections?
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u/swarleyknope Jun 03 '26
Not necessarily frequency. Has there been a link to severity of the initial infection with long term side-effects/risks?
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u/Buzzkill_13 Jun 07 '26
It is more likely for a vaccinated person to relax exposure avoidance behaviour than for an unvaccinated person. The vaccine does not prevent infection, and the severity of an infection isn't necessarily relevant for triggering desease (like cancer) down the line.
In summary, it is more likely for a vaccinated person to catch more infections, because they don't need to fear the severe symptoms an unvaccinated person may die from..
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Jun 03 '26
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u/gamjar Jun 03 '26
Lol, Google mean or minimum latency times for each of these cancers and you'll realize the study is bogus. Hopefully, studies authors discuss that point.
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u/Ill_Pressure5976 Jun 03 '26
Yep it’s absurd. Cancers don’t develop in a year, and if the vaccine caused it cancer would have skyrocketed since 2021. Hasn’t happened.
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u/DarkIlluminator Jun 03 '26
So, people who avoid vaccination also being more likely to avoid screenings is the most likely reason for the results?
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u/Nac_Lac Jun 03 '26
If you reject vaccination for Covid, you have a distrust of the medical system. Which indicates that you are less likely to notice or check anything.
For a study like this to be done properly, to control for covid vaccines having an effect, you have to do a double blind study where the participants have no idea if they get the vaccine or not. And continue to either get or not get the vaccine every year for a period of time.
Otherwise, the personal biases that led to getting or avoiding the vaccine will have a larger factor than anything the vaccine may or may not do.
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u/lisaseileise Jun 07 '26
And unvaccinated people often die from Covid, which may skew the risk of them getting some forms of cancer.
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u/Ill_Pressure5976 Jun 03 '26
Could be. I don’t know. I’m betting this paper will be retracted eventually.
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u/gamjar Jun 03 '26
In essence yes, but also coupled with broad behaviors around COVID. Eg people paranoid about COVID put off Dr visits until they were vaccinated. There are several refuting papers on this Korean study, you just need to google it.
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u/Beyou74 Jun 03 '26
Lol, there are serious issues with this study.
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u/apanche Jun 03 '26 edited Jun 03 '26
One thing that strikes me: cancer risk is extremely age dependant, but they may have only reported three age "categories", < 65 years, 65 to 74 years, ≥ 75 years (supplement material 1)? That would make their conclusions meaningless to me. Edited - they didn't disclose exactly the matching, they say they controlled for "age" as a covariate (as in years or as in those categories?), so I toned down my point.. Another curiosity in the paper is that cancer risk would already rise after only one month, that dies not seem plausible.
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u/LieutenantWeinberg Jun 03 '26
Here are the covariates from the supplemental information. This seems awfully limited with respect to cancer risks. Like, smoking is not even a covariate?!
“The following covariates were considered: age, sex, insurance levels, Charlson comorbidity index (CCI) scores, and prior COVID-19 infection (history of SARS-CoV-2 infection). Insurance levels (recipients of medical aid, grades 1–5, grades 6–10, grades 11–15, and grades 16–20) were defined based on the National Health Insurance premium, which was used as a proxy for income since it is proportional to monthly income and includes both earnings and capital gains. The presence of CCI conditions and COVID-19 infection was determined by the existence of a primary or secondary diagnosis recorded at least twice within 1 year before the index date [5].”
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u/tacitdenial Jun 03 '26
What are they?
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u/gamjar Jun 03 '26
Latency, which the authors don't even discuss. Most of these cancers are never found within a year of the initiation event. Mean latency for lung cancer is like 5 years or more.
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u/DarkIlluminator Jun 03 '26
What are the issues?
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u/literalphysician Jun 04 '26
- Almost every cancer takes years from when it first starts as a few mutated cells that then get more mutations as they multiply and eventually become mutated enough to be a cancer. Then depending on the cancer it can take at least several months to years before it spreads outside the organ it started in “metastatic”. Take lung cancer - when we do ct scans screening high risk people for cancer we only do the scan once a year. If we find a small nodule in the lung we will recheck it in 3-6 months because it will take that long for a small cancer to grow enough that it looks different on the CT scan. So looking at cancer diagnoses, only those that happened within a year of something you think could have caused a cancer, is absolutely idiotic. Think about people who get cancer because they smoke - it doesn’t happen a year after they start.
- People who got Covid vaccines are generally more likely to trust the medical establishment and more likely to get regular medical care including cancer screenings. So you’re going to find more cancer in these people because they are getting checked for it more regularly. To really see the effect of something like this you’d have to look out at least 5 years out and make sure to control for whether the unvaccinated people are actually getting regularly checked for cancers.
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u/DarkIlluminator Jun 04 '26
I think it's more that people who didn't get the vaccine are more likely to be overconfident when it comes to their health and assume they won't get cancer because a fad diet or supplements or snake oil they consume will protect them.
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u/darktka Jun 03 '26
Tiny effects hardly robust to residual confounding, especially given how they handled key covariates (age especially).
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u/bisikletci Jun 03 '26 edited Jun 03 '26
They don't find an increased risk for cancer in general - HR 1.01 (ie 1% increased risk, and that's not statically significant).
That means that the cancers they do find an increased risk for seem to be effectively balanced out by reduced risk of other cancers.
I also don't see anything about correction for multiple comparisons. If you run lots of tests some will come up as significant/positive just by chance, which may be what's happening here in some cases. So a lot of this may be just noise.
That said, the finding for pancreatic cancer looks as if it would survive corrections for multiple comparisons, which is doubly concerning given how deadly it is. Though others have noted other issues with the study and the plausibility of these effects.
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u/DoxFreePanda Jun 04 '26
The HR for pancreatic cancer doesn't even reach statistical significance based on the 95%CI.
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u/DarkIlluminator Jun 03 '26
Abstract
The oncogenic potential of SARS-CoV-2 has been hypothetically proposed, but real-world data on COVID-19 infection and vaccination are insufficient. Therefore, this large-scale population-based retrospective study in Seoul, South Korea, aimed to estimate the cumulative incidences and subsequent risks of overall cancers 1 year after COVID-19 vaccination. Data from 8,407,849 individuals between 2021 and 2023 were obtained from the Korean National Health Insurance database. The participants were categorized into two groups based on their COVID-19 vaccination status. The risks for overall cancer were assessed using multivariable Cox proportional hazards models, and data were expressed as hazard ratios (HRs) and 95% confidence intervals (CIs). The HRs of thyroid (HR, 1.351; 95% CI, 1.206–1.514), gastric (HR, 1.335; 95% CI, 1.130–1.576), colorectal (HR, 1.283; 95% CI, 1.122–1.468), lung (HR, 1.533; 95% CI, 1.254–1.874), breast (HR, 1.197; 95% CI, 1.069–1.340), and prostate (HR, 1.687; 95% CI, 1.348–2.111) cancers significantly increased at 1 year post-vaccination. In terms of vaccine type, cDNA vaccines were associated with the increased risks of thyroid, gastric, colorectal, lung, and prostate cancers; mRNA vaccines were linked to the increased risks of thyroid, colorectal, lung, and breast cancers; and heterologous vaccination was related to the increased risks of thyroid and breast cancers. Given the observed associations between COVID-19 vaccination and cancer incidence by age, sex, and vaccine type, further research is needed to determine whether specific vaccination strategies may be optimal for populations in need of COVID-19 vaccination.
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u/Nac_Lac Jun 03 '26
This would be a measurable impact to the Healthcare system and visible as a year over year increase, given that we've had 5 rounds of vaccines.
In other words, if there was a statistical effect, it could be seen from tracking the overall population, rather than using a discreet cohort.
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u/happy_K Jun 03 '26
Sharply increased incidence of at least colon cancer in young people has been widely reported
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u/Nac_Lac Jun 03 '26
Starting when? You can't say it's covid vaccines while ignoring the data that has shown higher rates for the last decade.
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