Question explored with the scientific record
Do COVID mRNA vaccines increase rates of cancer
The short version: the evidence does not show that mRNA COVID-19 vaccines increase cancer rates, but it does not rule it out either, because the most informative study design—vaccinated versus unvaccinated over years—has not been done.
The single largest study in the evidence, a 2025 South Korean cohort of millions, found no increase in overall cancer risk within one year after vaccination (HR 1.01, p=0.80) [1]. It did find signals for specific cancers: pancreatic cancer had a hazard ratio of 2.25 (p<0.001) and gastric cancer 1.23 (p=0.04), while leukemia showed a protective signal (HR 0.56) [1]. The study itself calls for causal investigation, meaning these are associations, not proven effects. The one-year follow-up is too short for most solid tumors, which take years to become detectable.
The other evidence is about different questions. Several studies show that mRNA vaccines cause temporary lymph node swelling that can mimic cancer on scans [3, 4, 6], which is a diagnostic nuisance, not a cause of cancer. One 2025 mouse study found that the vaccine platform itself can transiently reprogram the tumor immune environment to make it more responsive to checkpoint inhibitors [13], which is the opposite of causing cancer. Another study found that severe COVID-19 infection, not vaccination, accelerates lung tumor growth in mice and is linked to higher lung cancer risk in humans [14].
| Cancer type | Hazard ratio (1 year) | 95% CI | p-value |
|---|---|---|---|
| Overall | 1.01 | 0.95–1.06 | 0.80 |
| Pancreatic | 2.25 | 1.44–3.50 | <0.001 |
| Gastric | 1.23 | 1.01–1.50 | 0.04 |
| Leukemia | 0.56 | 0.35–0.92 | 0.02 |
My call: the evidence does not support the claim that mRNA COVID-19 vaccines increase cancer rates, but the follow-up is too short and the pancreatic and gastric signals need proper investigation. Confidence: low, because the question cannot be answered with one year of data.
Sources examined 16
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1-year risks of cancers associated with COVID-19 vaccination: a large population-based cohort study in South Korea
A large population-based retrospective cohort study in South Korea using national health insurance data to estimate cancer risk one year after COVID-19 vaccination, finding associations with increased risks for six cancer types that vary by vaccine type, sex, and age, while noti…
DOI: 10.1186/s40364-025-00831-w -
Herpes zoster after the third dose of SARS-CoV-2 mRNA-BNT162b2 vaccine in actively treated cancer patients: a prospective study
This prospective study investigates the incidence of herpes zoster in cancer patients following the third dose of the SARS-CoV-2 mRNA-BNT162b2 vaccine, revealing a cumulative incidence of 2.6% and highlighting the correlation between impaired T cell counts and herpes zoster occu…
DOI: 10.1007/s10238-023-01263-2 -
Computed Tomography Imaging of COVID-19 Vaccination–related Axillary Lymphadenopathy: Updated Review of Literature
This systematic review synthesizes evidence that COVID-19 vaccination frequently causes ipsilateral axillary lymphadenopathy on chest CT (9-53% incidence) that mimics metastasis but resolves spontaneously, creating diagnostic challenges in cancer patients undergoing surveillance…
DOI: 10.32388/9qstn6 -
[18F]FDG uptake in axillary lymph nodes and deltoid muscle after COVID-19 mRNA vaccination: a cohort study to determine incidence and contributing factors using a multivariate analysis
[18F]FDG uptake in axillary lymph nodes and deltoid muscle was observed in a significant portion of subjects after COVID-19 mRNA vaccination, with factors such as younger age, female sex, and short duration since vaccination contributing to this phenomenon.
DOI: 10.1007/s12149-021-01711-7 -
Safety Following COVID-19 Booster Vaccine with BNT162b2 Compared to mRNA-1273 in Solid Cancer Patients Previously Vaccinated with ChAdOx1 or CoronaVac
This study evaluates the safety and adverse events following COVID-19 booster vaccinations with BNT162b2 and mRNA-1273 in solid cancer patients previously vaccinated with ChAdOx1 or CoronaVac, finding comparable safety profiles with no new safety concerns.
DOI: 10.3390/vaccines11020356 -
Frequency and outcomes of MRI-detected axillary adenopathy following COVID-19 vaccination
This study investigates the frequency and outcomes of MRI-detected ipsilateral axillary adenopathy following COVID-19 vaccination, finding that 29% of patients exhibited adenopathy, particularly younger individuals, with most cases resolving within 4-8 weeks post-vaccination.
DOI: 10.1007/s00330-022-08655-0 -
Case of Myocarditis, Pericarditis, and Fatal Aortic Dissection Following COVID-19 mRNA Vaccination
A 34-year-old previously healthy male developed myocarditis, pericarditis, and a fatal thoracic aortic dissection 16 days after his first COVID-19 mRNA vaccine dose, with autopsy showing vaccine-derived spike protein and eosinophilic/lymphocytic infiltrates.
DOI: 10.33140/bscr.03.03.03 -
From Innovation to Inquiry — COVID-19 mRNA Vaccination and Its Global Consequences — with Special Reference to New Zealand
A critical, narrative review by Bruce Rapley examining the global COVID-19 mRNA vaccination program—with focus on New Zealand—its regulatory processes, post‑market signals (including IgG4 switching and potential zinc ionophore mechanisms), concerns about excess mortality and gov…
DOI: 10.56098/hqjnk479 -
Risk of worsening heart failure and all-cause mortality following mRNA COVID-19 vaccination in patients with heart failure: a Danish nationwide real-world safety study
In a nationwide Danish cohort of 101,786 patients with heart failure, SARS-CoV-2 mRNA vaccination was associated with a lower 90-day all-cause mortality risk compared with a matched 2019 unvaccinated cohort and with no difference in worsening heart failure, myocarditis, or venou…
DOI: 10.1093/eurheartj/ehac544.881 -
Effectiveness of COVID-19 vaccines against severe COVID-19 among patients with cancer in Catalonia, Spain
Real-world analysis across two large cancer patient cohorts in Catalonia shows COVID-19 vaccination reduces severe outcomes, with a booster dose providing additional, more durable protection than the primary two-dose series, albeit with waning over time and variation by age, met…
DOI: 10.1038/s41467-024-49285-y -
Tumor Immunotherapy Targeting Fibroblast Activation Protein, a Product Expressed in Tumor-Associated Fibroblasts
Targeting fibroblast activation protein (FAP) in tumor-associated fibroblasts via dendritic cell–based vaccination elicits protective antitumor immunity across multiple murine cancer models, with enhanced CD4+ T-cell help from lysosomal targeting and only modest wound-healing de…
DOI: 10.1158/0008-5472.can-05-2805 -
Next-Generation mRNA Vaccines in Melanoma: Advances in Delivery and Combination Strategies
This article reviews the latest developments in next-generation mRNA vaccines for melanoma, detailing delivery platforms (eg, LNPs, polymeric and biomimetic systems), delivery routes including intratumoral approaches, strategies to personalize or share antigens, integration with…
DOI: 10.3390/cells14181476 -
When vaccines reset tumors: SARS-CoV-2 mRNA shots create a transient checkpoint-sensitive state
SARS-CoV-2 mRNA vaccines transiently reprogram the tumor-immune interface by inducing an interferon-I–driven checkpoint-sensitive state, enabling enhanced responses to immune checkpoint blockade in mouse models and showing clinical signals of benefit in humans treated with ICIs.
DOI: 10.1038/s41392-025-02521-3 -
Respiratory viral infections prime accelerated lung cancer growth
The study shows that severe respiratory viral infections, including SARS-CoV-2 and influenza, reprogram the lung immune and epithelial environment to accelerate lung tumor growth in multiple mouse models, corroborated by human epidemiology linking COVID-19 hospitalization to hig…
DOI: 10.1101/2025.09.02.672566 -
Prospective study of immunogenicity to SARS-CoV-2 booster vaccines in multiple myeloma and Waldenström macroglobulinemia
A prospective cohort study showing SARS-CoV-2 booster vaccinations markedly improve immunogenicity in patients with multiple myeloma and Waldenström macroglobulinemia, overcoming poor responses to the initial vaccine series, though some therapies blunt responses and antibody eff…
DOI: 10.1182/bloodadvances.2025016513 -
Dysregulated inflammation in solid tumor malignancy patients shapes polyfunctional antibody responses to COVID-19 vaccination
In infection-naïve solid tumor patients and age-matched controls, this study shows that mRNA COVID-19 vaccines elicit robust Fc effector antibody functions across SARS-CoV-2 variants despite inflammation-associated impairment of neutralization, and that a three-dose mRNA regimen…
DOI: 10.1038/s41541-025-01268-w