DoubleChecks

What was claimed

About a month after my second Pfizer vaccine, my skin cancer came back like wildfire... There is a published study involving more than 8 million people... higher rate of several cancers after the COVID vaccination.

Our verdict

Inaccurate

Multiple authoritative sources including the National Cancer Institute and medical literature explicitly state there is no evidence that COVID-19 vaccines cause cancer, lead to recurrence, or disease progression. A temporal sequence alone cannot show that the vaccine caused recurrence. The National Cancer Institute states that there is no evidence COVID-19 vaccines cause cancer, recurrence, or disease progression.

1 of 3 AI systems agree15 sources citedChecked Oct 6, 2026

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Key findings

COVID-19 vaccines cause cancer recurrence

Incorrect98%
1 AI checked

"About a month after my second Pfizer vaccine, my skin cancer came back like wildfire..." (implied causal link)

Can’t verify75%
All 3 AIs agree

There is a published study involving more than 8 million people that reported higher rates of several cancers after COVID vaccination.

Verified92%
2 of 4 AIs agree·Claude: Misleading, Perplexity: Misleading

Verified against 15 sources

cancer.govbreastcancer.orgfactcheck.orgmskcc.orgfactcheck.orgpubmed.ncbi.nlm.nih.govsnopes.comleadstories.comada.compmc.ncbi.nlm.nih.govfactcheck.orgedocs.buttecounty.ca.govgeneticliteracyproject.orgpmc.ncbi.nlm.nih.govascopubs.org

Detailed Analysis

A South Korean retrospective study of 8,407,849 people reported associations between vaccination and higher one-year incidence of six cancers. However, the study does not establish that vaccination caused cancer, and authoritative cancer sources state there is no evidence that COVID-19 vaccines cause cancer, recurrence, or progression. The personal claim that skin cancer returned one month after Pfizer vaccination is therefore unverified and cannot establish causation.

Why this verdict

  • A South Korean retrospective study of 8,407,849 people reported associations between vaccination and higher one-year incidence of six cancers.
  • However, the study does not establish that vaccination caused cancer, and authoritative cancer sources state there is no evidence that COVID-19 vaccines cause cancer, recurrence, or progression.
  • The personal claim that skin cancer returned one month after Pfizer vaccination is therefore unverified and cannot establish causation.

Claims checked

The study shows that COVID vaccination causes higher rates of several cancers.

Misleading94%
The study reported associations and acknowledged the need for further research; it did not establish causation. Confounding, detection differences, and other methodological limitations can produce such associations.

This claim may mislead readers without added context.

COVID vaccination caused the person’s skin cancer to return about one month after a second Pfizer dose.

Can’t verify91%
A temporal sequence alone cannot show that the vaccine caused recurrence. The National Cancer Institute states that there is no evidence COVID-19 vaccines cause cancer, recurrence, or disease progression.

There is a published study involving more than 8 million people that reported higher rates of several cancers after COVID vaccination.

Verified93%
A 2025 South Korean retrospective cohort study analyzed 8,407,849 people and reported higher rates of thyroid, gastric, colorectal, lung, breast, and prostate cancers within one year after vaccination. This is an observational association, not proof that vaccination caused the cancers.

What other AI think

The statement selectively cites a real study but misrepresents its findings and conclusions. While an 8-million-person study exists, its authors explicitly stated their findings should not be interpreted as evidence of vaccine-induced cancer risk. The overall claim implies causation where none has been established by credible evidence.

Why this verdict

  • The statement selectively cites a real study but misrepresents its findings and conclusions.
  • While an 8-million-person study exists, its authors explicitly stated their findings should not be interpreted as evidence of vaccine-induced cancer risk.
  • The overall claim implies causation where none has been established by credible evidence.

Claims checked

COVID-19 vaccines cause cancer recurrence

Incorrect98%
Multiple authoritative sources including the National Cancer Institute and medical literature explicitly state there is no evidence that COVID-19 vaccines cause cancer, lead to recurrence, or disease progression.

This claim may mislead readers without added context.

There is a published study involving more than 8 million people showing higher rate of several cancers after COVID vaccination

Misleading95%
A South Korean study of 8+ million people exists and reported associations between vaccination and certain cancers. However, the study's authors explicitly stated these are epidemiologic associations only, not causal evidence. The study followed people for only one year, insufficient for cancer causation claims.

This claim may mislead readers without added context.

Skin cancer recurrence occurred after second Pfizer vaccine

Can’t verify50%
This is a personal anecdote that cannot be verified. Temporal association (cancer appearing after vaccination) does not establish causation, especially given the lack of evidence for vaccine-induced cancer.
One large population study reporting associations between COVID-19 vaccination and higher incidence of certain cancers does exist, but its findings are observational and do not demonstrate causation. The personal anecdote about a cancer recurrence after vaccination is unverifiable and cannot establish a causal link.

Why this verdict

  • One large population study reporting associations between COVID-19 vaccination and higher incidence of certain cancers does exist, but its findings are observational and do not demonstrate causation.
  • The personal anecdote about a cancer recurrence after vaccination is unverifiable and cannot establish a causal link.

Claims checked

"About a month after my second Pfizer vaccine, my skin cancer came back like wildfire..." (implied causal link)

Can’t verify85%
This is a single-person anecdote with no verifiable medical records or timeline; temporal proximity alone does not establish causation and cannot be confirmed from the provided text.

"There is a published study involving more than 8 million people... higher rate of several cancers after the COVID vaccination."

Verified90%
A South Korean population‑based cohort study of roughly 8.4 million people reported associations between COVID‑19 vaccination and increased incidence of several cancer types, though the study is observational and authors caution it cannot prove causation.

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