What independent validations or reanalyses of the 2025 Seoul cancer–vaccine cohort have been published?
Executive summary
The Seoul 2025 cohort study linking COVID-19 vaccination to a higher 1‑year cancer incidence has prompted several independent critiques, methodological reanalyses and media dissections rather than a single formal, peer‑reviewed replication; notable independent responses include a non‑peer‑reviewed quantitative reanalysis challenging incidence calculations, a methodological critique proposing an External Validity Consistency Condition (EVCC), and multiple expert reviews that highlighted serious design limitations and potential biases [1] [2] [3]. The original paper’s supplementary data were posted openly and the journal has notified readers that concerns have been raised and will be investigated, providing the raw materials that critics used for reanalysis [4] [5] [6].
1. The original Seoul cohort and what it released
The study itself — “1‑year risks of cancers associated with COVID‑19 vaccination” — reported epidemiological associations between vaccination and cancer incidence using Seoul health insurance records and published supplementary files on Figshare, which made patient‑level aggregates and analytic appendices available for outside scrutiny [6] [4] [5]. The journal’s article metrics page and notices confirm that readers have been alerted to concerns about the work and that editorial action is pending, meaning the original dataset and materials are publicly in play while formal correction or retraction processes proceed [7] [6].
2. Quantitative reanalyses and preprints challenging the incidence signal
An independent, non‑peer‑reviewed short note recalculated crude incidence rates from the study’s raw figures and argued the reported cancer signal was inconsistent with national cancer registry benchmarks, presenting numerical reanalysis that called cohort representativeness into question [1]. Separately, a methodological paper introduced the EVCC — External Validity Consistency Condition — and applied that framework to this Seoul cohort as an example, concluding that large registry‑based cohorts can generate internally consistent but externally non‑representative risk signals and urging quantitative checks against national benchmarks [2]. Both pieces function as reanalyses: the short note recalculated rates from the authors’ figures, and the EVCC paper reinterpreted the cohort through a formal external‑validity test [1] [2].
3. Expert reviews and fact‑checking that dissect methods rather than confirm results
Journalistic and fact‑checking outlets and specialist reviewers evaluated the study’s design and public claims: ScienceFeedback published a methodological review concluding the study contained significant shortcomings that undermine its validity; that critique emphasized confounding, selection and interpretation problems typical of retrospective cohorts and warned against causal language [3]. MedPage Today summarized expert opinion asserting the retrospective Korean analysis “proves nothing” about causation and highlighted phenomena like unmasking (where healthcare contacts for vaccination lead to incidental diagnoses) as alternate explanations for observed associations [8]. Al Jazeera’s reporting also stressed that the study showed associations and not causation and quoted WHO officials reiterating that observational studies generate hypotheses but do not establish causality [9].
4. Systematic reviews and how the Seoul cohort fits into broader literature
A broader literature synthesis published in Oncotarget catalogued global case reports and two population‑level retrospective investigations — one from Italy and the Seoul cohort — as part of a set of studies examining potential post‑vaccination cancer signals, treating the Korean analysis as one of few large population‑level studies and urging more longitudinal, mechanism‑focused research to resolve whether observed signals are artefacts or meaningful trends [10]. That review situates the Seoul cohort within a sparse and contested body of work rather than treating it as a definitive replication of an effect.
5. Where the independent work leaves investigators and the public
The independent activity to date is primarily critique, recalculation and contextualization — a short non‑peer‑reviewed reanalysis of incidence rates, a methodological EVCC paper, formal reviews by fact‑checkers and clinical‑epidemiology commentators, plus media scrutiny — but no published independent, peer‑reviewed replication that reproduces the study’s principal claim has appeared in the sources provided [1] [2] [3] [8] [9]. The openly posted supplements from the authors and the journal’s reader alerts have enabled these reanalyses, and the literature summaries call for further well‑designed longitudinal and mechanistic studies to adjudicate the question definitively [4] [5] [10].