TL;DR: A study of 8.4 million people in South Korea found a link between COVID-19 vaccination and increased risk of six types of cancer after one year. Experts stress the findings show correlation, not causation, and more research is needed.
🔹 Key Findings from the Study
- Increased Cancer Risk Found Post-Vaccination
- A retrospective study of 8,407,849 individuals in South Korea (2021-2023) found increased one-year cancer incidence in vaccinated vs. unvaccinated groups.
- Cancer types with significantly elevated hazard ratios (HRs):
- Thyroid: HR 1.351
- Gastric (stomach): HR 1.335
- Colorectal: HR 1.283
- Lung: HR 1.533
- Breast: HR 1.197
- Prostate: HR 1.687
- Different Risks by Vaccine Type
- cDNA vaccines linked to thyroid, gastric, colorectal, lung, and prostate cancers.
- mRNA vaccines linked to thyroid, colorectal, lung, and breast cancers.
- Heterologous vaccination (mixing types) linked to thyroid and breast cancers.
- Study Design Details
- Published in Biomarker Research on September 25, 2025.
- Used Korean National Health Insurance data.
- Retrospective, observational cohort study using Cox proportional hazards models.
- Final matched sample: 2.38 million people (595,007 vaccinated).
🔹 Expert Reactions and Limitations
- Causation Not Established
- Researchers emphasized: “associations were observed, but the results do not prove causality.”
- Potential detection bias and confounding factors could influence results.
- One-year follow-up considered too short for typical cancer development by some experts.
- Scientific and Public Response
- Dr. Vinay Prasad (UCSF) noted potential surveillance bias in vaccinated populations.
- Dr. Benjamin Major (Johns Hopkins) said the short time frame makes a direct link unlikely.
- WHO and CDC have not confirmed any causal connection between COVID-19 vaccines and cancer.
- Public Health Context
- Despite findings, researchers and global health agencies continue to affirm that COVID-19 vaccines are essential for preventing severe disease and death.
- The study authors called for further research to explore long-term effects and optimize vaccination strategies.
SOURCE : https://pubmed.ncbi.nlm.nih.gov/41013858/#:~:text=The oncogenic potential of,of COVID-19 vaccination.