In 2025 a Korean study was passed around online as proof that COVID vaccines cause cancer. Its own authors said it proved no such thing. Now a study of 36 million people has looked again and found no spike.
By Joseph J. Jackson | Florida Man News Network | Nov. 11, 2026
In late September 2025, a headline raced across social media: "Study of 8 Million Confirms Deadly Cancers Surging Among Covid-Vaxxed."
The posts under it listed big numbers: lung cancer up 53%, prostate cancer up 69%, overall cancer risk up 27%. They called it proof of the "turbo cancer" epidemic. A European Parliament member repeated it. The Daily Mail ran with it.
If you only read the headline, the question looked settled. If you read the study, it said something very different. And last month, a far larger study from the same country answered the question again.
The rating: MISLEADING. The 2025 study found a statistical link over one year. It did not show that vaccines cause cancer, and its authors said so in writing. A nationwide study of 36 million people published Oct. 22, 2026, found no rise in cancer after South Korea's vaccine rollout.
What the 2025 study actually said
The paper was published Sept. 26, 2025, in the journal Biomarker Research. It was not a full research article. It was a short letter to the editor, from a team led by Dr. Eun Mi Chun of Ewha Womans University Mokdong Hospital in Seoul.
The team used national health insurance records for about 8.4 million people in Seoul from 2021 to 2023. They compared vaccinated and unvaccinated groups and found that vaccinated people were diagnosed with six cancers more often in the year after their shots: thyroid, stomach, colorectal, lung, breast and prostate.
The authors called that an "association." Their supplementary file, published alongside the paper, says plainly: "our findings do not establish causal relationships."
So the word "confirms" in that viral headline came from the people sharing it, not from the researchers.
What the headlines left out
One year is too short. Solid tumors usually take years to grow large enough to be found. Experts quoted in fact checks by Full Fact and others said it isn't medically plausible for a vaccine to cause a solid tumor that gets diagnosed within a year.
People who get vaccinated also get checked more. People who get vaccines also tend to keep up with checkups and cancer screenings, and South Korea runs strong screening programs, especially for older and high-risk people. When you look harder, you find more. That's called surveillance bias, and the study wasn't designed to rule it out.
Key risk factors were missing. Analysts on the BBC's More or Less pointed out that the study didn't account for things like smoking, genetics or a past cancer diagnosis.
The journal itself flagged it. Biomarker Research later added a note at the top of the paper alerting readers that "concerns with this article have been raised with the Editors," and saying it would act once those concerns were investigated. In March 2026 the journal published a commentary from Belgian researchers questioning the study's methods.
Even a major tabloid had to correct itself. The Daily Mail corrected its story after it wrongly reported that the Korean researchers said they had found "proof" that vaccines raised cancer risk, according to the UK fact-checker Full Fact.
South Korea's own health agency disagreed. The Korea Disease Control and Prevention Agency said the study didn't prove cause and effect, and kept recommending vaccines for older and high-risk people.
The bigger test: 36 million people, 50 months
On Oct. 22, 2026, a team from Korea University College of Medicine, led by Professor Jaehun Jung, published a much larger study in the same journal: "Impact of SARS-CoV-2 vaccination on cancer trends: a nationwide interrupted time series study."
The design asked a simple question. If vaccines really caused a big, fast jump in cancer, wouldn't it show up in the national numbers?
Who was studied: National Health Insurance Service records for 36,024,394 people born from 1955 to 2004, about 89% of whom got at least one dose.
Time covered: February 2011 through September 2025, nearly 15 years of monthly cancer data.
The test: Researchers compared cancer rates in the 50 months after August 2021, when mass vaccination began, with what the previous decade's trends predicted. They also ran the same test at 30 fake "start dates" before the pandemic, to make sure the method wasn't just finding noise.
The result: No sudden jump and no faster climb in any of 13 cancer categories. Separate checks of the four cancers the earlier study flagged most, stomach, colorectal, lung and prostate, came back the same.
At a science media briefing on Oct. 29, Jung said such a change was not seen in nationwide trends, and argued that if the vaccine effect were as big as the earlier study suggested, it would have shown up in a country where almost everyone is vaccinated.
A separate Korean study published Sept. 10, 2026, matched about 1.19 million AstraZeneca recipients with the same number of Pfizer or Moderna recipients. Over about three years, it found no meaningful difference in risk across 12 cancer types, EDAILY reported.
What the new study doesn't prove, either
We hold every study to the same standard, including the ones that reassure us.
The Korea University team says its results don't fully settle long-term risk, and that the drop in cancer screening during the pandemic, and the rebound afterward, are hard to rule out completely. They say more follow-up is needed. The study looks at the whole population, not at individual patients.
What it does show is that the "surge" described in those 2025 headlines didn't happen in South Korea's national cancer numbers.
Why a bad headline does real damage
Dr. Eom Joong-sik, an infectious disease professor at Gachon University Gil Medical Center, told Korean reporters that some older and immunocompromised patients have refused vaccines over cancer fears since the 2025 paper spread. Those are the people COVID still hospitalizes and kills.
A headline can be shared in two seconds. Its effects on people's health can last for years.
How to read past the headline
You don't need a science degree. Ask six questions:
Click through. Is it a full study or a short letter to the editor?
Find the verb. Does the study say "associated with" or "causes"? They mean different things.
Check the time frame. Could the effect being claimed actually happen in that amount of time?
Look for a journal note. Has the journal added a warning, correction or expression of concern?
Ask the big-picture question. If this were true, what else would we see? Here, it would have been a national cancer spike. There wasn't one.
Look at who's sharing it. Are they the researchers, or accounts that have spread vaccine misinformation before?
The bottom line
The 2025 study found a one-year statistical link and said in writing that it couldn't prove cause. The journal flagged it, a newspaper corrected its coverage of it, and a study more than four times larger, covering almost 15 years of national data, found no cancer surge.
Headlines don't always tell the truth. Read the story. Read the sources. Then decide.
Sources
Na Y., Radnaabaatar M., Jung J., "Impact of SARS-CoV-2 vaccination on cancer trends: a nationwide interrupted time series study," Biomarker Research 14:147 (Oct. 22, 2026): https://doi.org/10.1186/s40364-026-01027-6
EDAILY, "Does Getting the COVID-19 Vaccine Cause Cancer? A 50-Month Follow-Up Study Reveals" (Oct. 29, 2026): https://en.edaily.co.kr/news/eda202610295434/
Kim H.J., Kim M.-H., Choi M.G., Chun E.M., "1-year risks of cancers associated with COVID-19 vaccination: a large population-based cohort study in South Korea," Biomarker Research 13:114 (2025), with the journal's note to readers: https://doi.org/10.1186/s40364-025-00831-w
Full Fact, "Daily Mail corrects article about Covid vaccines and cancer" (Oct. 6, 2025): https://fullfact.org/health/mail-covid-vaccines-cancer-korea/
Al Jazeera, "Did a South Korean study really claim that COVID-19 vaccines cause cancer?" (Oct. 11, 2025): https://www.aljazeera.com/features/2025/10/11/did-a-south-korean-study-really-claim-that-covid-19-vaccines-cause-cancer
Asia Economy, KDCA says causality not proven (Oct. 13, 2025): https://cm.asiae.co.kr/en/article/2025101321370451298
BBC More or Less, episode summary via Station LM: https://stationlm.com/analysis/16e5b01c-b1ec-4cd8-909a-35d9a9764067