Question explored with the scientific record
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- 1 having or mixing phizer and astra zeneca covid vaccines have shown to activate turbo cancers
- 2 Are there any studies on cancer risk after COVID vaccines overall?
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Are there any studies on cancer risk after COVID vaccines overall?
The short version: one large South Korean study found no increase in overall cancer risk within one year after COVID-19 vaccination, but it did find higher risks for several specific cancers that demand explanation.
The best evidence on your question is a 2025 population-based cohort study from South Korea that followed over 8 million people for one year after vaccination using national health insurance data [3]. It found the overall cancer hazard ratio was 1.01, meaning no increased risk for cancer as a whole. That is a large, well-designed study with a true comparison group.
But the results for individual cancer types are not uniform. Pancreatic cancer showed a hazard ratio of 2.25 (p < 0.001), gastric cancer showed 1.23 (p = 0.041), and leukemia showed a significantly reduced risk at 0.56 (p = 0.02). These patterns varied by vaccine type, sex, and age [3]. The authors themselves noted the need for causal investigation and pointed out limitations.
| Cancer type | Hazard ratio | 95% CI | p-value |
|---|---|---|---|
| Overall cancer | 1.01 | 0.95–1.06 | 0.803 |
| Pancreatic cancer | 2.25 | 1.44–3.50 | <0.001 |
| Gastric cancer | 1.23 | 1.01–1.50 | 0.041 |
| Leukemia | 0.56 | 0.35–0.92 | 0.020 |
| Non-Hodgkin lymphoma | 0.76 | 0.57–1.00 | 0.053 |
| Hodgkin lymphoma | 3.01 | 0.36–25.01 | 0.308 |
The other studies in the evidence do not address new-onset cancer risk. Most of them look at how vaccines perform in people who already have cancer [1, 2, 4, 6, 7, 8, 9, 10, 11, 12], which is a different question. One case series of five patients reported cancers appearing after vaccination but had no control group [5]. Another small Quebec study found 31 cancer diagnoses among 112 vaccinated adults but could not separate causation from coincidence [13]. Neither proves anything on its own.
The South Korean study [3] is the strongest evidence here. It covers one year only. Cancer can take years to develop. One year of follow-up may be too short to detect a signal, especially for slow-growing tumors. A single study, no matter how large, does not settle the question. The association with pancreatic cancer is striking and warrants independent replication, but it could also be a chance finding given the number of cancer types tested.
My call: the evidence does not show an increased overall cancer risk within one year after COVID-19 vaccination, but it flags specific cancer types—especially pancreatic cancer—that need much longer follow-up and independent confirmation. Confidence: moderate for no overall effect; low for the individual cancer findings, because one year is too short and the associations have not been replicated.
Sources used 13
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Role of COVID-19 Vaccine in the Management of Gynecologic Oncology Lymphadenopathies
This study evaluates the incidence of lymphadenopathies following COVID-19 vaccination in gynecologic oncology patients, finding no significant increase in incidence or impact on clinical management compared to non-vaccinated patients.
DOI: 10.3390/ijerph21081063 -
COVID-19 Infection After Different Combinations of Vaccines in Patients with Solid Tumors
This study evaluates the incidence of COVID-19 infection in cancer patients after receiving different combinations of COVID-19 vaccines, revealing similar efficacy across vaccine types but highlighting a significant time from vaccination to infection in patients undergoing cytot…
DOI: 10.14744/ejmi.2023.31704 -
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 -
Safety of COVID-19 vaccines in subjects with solid tumor cancers receiving immune checkpoint inhibitors
A retrospective chart review of 284 solid-tumor cancer patients on immune checkpoint inhibitors who received COVID-19 vaccines found no increased risk of severe immune-related adverse events, supporting the safety of vaccination during ICI therapy.
DOI: 10.1080/21645515.2023.2207438 -
Which Could Be the Risk Factors for Developing Cancer After Receiving The COVID-19 Vaccine?
In a five-case series, cancers appeared days-to-months after COVID-19 vaccination; the author attributes a shared TCM energy deficiency as risk factor and recommends TCM treatment, but no controls or statistics support causation.
DOI: 10.33140/ijcrt.08.01.01 -
COVID-19 Vaccination in Patients with Hematological Malignances
A narrative review synthesizing how COVID-19 vaccination affects patients with hematological malignancies (HM), highlighting booster-driven improvements in seroconversion and immune responses, the persistence of suboptimal responses in anti-CD20–treated, HSCT, and CAR-T–treated …
DOI: 10.3390/vaccines13050465 -
The Efficacy and Immunogenicity of COVID-19 Vaccine: Special Focus on Patients with Cancer
COVID-19 vaccines are generally safe for cancer patients, but vaccine-induced immunogenicity is often reduced—especially in hematologic malignancies and patients on B-cell–depleting therapies—necessitating booster doses and tailored vaccination strategies.
DOI: 10.54963/ti.v9i3.1017 -
Risk of SARS-CoV-2 Breakthrough Infection in Vaccinated Cancer Patients: A Retrospective Cohort Study
In 9417 vaccinated cancer patients, the breakthrough infection rate was 1.1% during the delta variant surge; 27% of breakthrough infections required hospitalization and 5% were fatal, with higher risk in hematologic malignancy, multiple myeloma, and antineoplastic therapy.
DOI: 10.1186/s13045-022-01290-8 -
Pre-vaccine immune profiling in cancer patients identifies correlates of COVID-19 vaccine responses
Pre-vaccine immune profiling in cancer patients on active treatment identifies specific pre-existing B- and T-cell features and innate immune signatures that correlate with both humoral and TCR-based cellular responses to SARS-CoV-2 mRNA vaccines, suggesting immune fitness bioma…
DOI: 10.1080/21645515.2025.2599622 -
COVID-19 Breakthrough Infections Among Patients with Cancer Receiving Sinopharm BBIBP-CorV Vaccine
A retrospective study from Isfahan, Iran, evaluating COVID-19 breakthrough infections in cancer patients fully vaccinated with Sinopharm BBIBP-CorV, finding 9 breakthrough cases (4.1% of vaccinated cancer patients with COVID-19) with notable hospitalization and mortality, especi…
DOI: 10.5812/ijcm-123887 -
Safety and antibody response to two-dose SARS-CoV-2 messenger RNA vaccination in patients with multiple myeloma
This study evaluates the safety and antibody response to two-dose SARS-CoV-2 mRNA vaccination in patients with multiple myeloma, finding high rates of seroconversion and mild reactogenicity.
DOI: 10.1186/s12885-021-09097-5 -
Immune Response to COVID-19 Vaccination in Children With Cancer
Prospective multicenter cohort study in Australian children and adolescents with cancer (SerOzNET) evaluating immune responses to BNT162b2 vaccination across 2 and 3 doses, showing substantial neutralizing antibody and T-cell IFN-γ responses even during active cancer treatment w…
DOI: 10.1542/peds.2024-070209 -
A 6-Week Time Period May not be Sufficient to Identify Potential Adverse Events Following COVID-19 Vaccination
A retrospective observational study of 112 adults vaccinated against COVID-19 in Quebec shows that the majority of health-related events recorded in pharmacy records occur after 6 weeks post-vaccination, suggesting the current 6-week adverse event reporting window is insufficien…
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