No Significant Increase in Cancer Incidence Following COVID-19 Vaccination
There is no evidence of a significant increase in cancer incidence caused by COVID-19 vaccination. The most recent and highest quality population-based study from the United States analyzed 693 unique cancer types and found no support for increased cancer incidence in 2021 due to the COVID-19 pandemic or vaccination 1.
Key Evidence Against Increased Cancer Risk
US Population-Based Surveillance Data (2025)
The Surveillance, Epidemiology, and End Results (SEER-22) database analysis of 693 individual cancer types found only nine cancer types with statistically significant increases in 2021 compared to 2018-2019, and all nine increases were attributed to changes in cancer registry reporting practices, not actual disease increases 1.
Cancer types of particular concern in media reports—including cholangiocarcinoma, diffuse large B-cell lymphoma, Kaposi sarcoma, and lung cancer—did not show increased incidence during 2021 1.
The study specifically evaluated the period when COVID-19 vaccination was widely deployed and found no evidence supporting carcinogenic effects of SARS-CoV-2 infection or vaccination 1.
Contradictory Evidence Requires Critical Evaluation
- A 2025 South Korean study reported increased hazard ratios for several cancers at 1 year post-vaccination 2, but this study has significant methodological limitations that undermine its conclusions:
- The study design cannot establish causation between vaccination and cancer development
- The 1-year timeframe is biologically implausible for vaccine-induced carcinogenesis
- The findings conflict with larger, more rigorous US surveillance data 1
- Confounding factors related to healthcare access patterns during the pandemic were not adequately controlled
Understanding the Pandemic's True Impact on Cancer Rates
Delayed Diagnoses, Not Increased Incidence
The COVID-19 pandemic caused substantial declines in cancer incidence rates in 2020 due to disruptions in screening and diagnostic services, not because fewer cancers occurred 3.
By 2021, cancer incidence rates returned close to prepandemic levels for most cancer sites, but did not show the expected rebound that would incorporate delayed 2020 diagnoses 3.
Metastatic breast cancer was an exception, showing significantly higher observed rates than expected in 2021 (rate ratio = 1.09,95% CI 1.04-1.13), likely reflecting progression of undiagnosed cancers during pandemic-related care delays 3.
Clinical Context: Vaccination Remains Essential for Cancer Patients
Protective Benefits Outweigh Theoretical Concerns
COVID-19 vaccination significantly reduces hospitalization and death in cancer patients by 56% (odds ratio 0.44,95% CI 0.28-0.72) 4, 5.
Cancer patients face 10-fold higher mortality from COVID-19 infection compared to the general population, making vaccination a critical protective intervention 4.
The American Society of Clinical Oncology, National Comprehensive Cancer Network, and European Society for Medical Oncology all strongly recommend COVID-19 vaccination for all eligible cancer patients 4, 5.
Vaccine Safety Profile in Cancer Populations
The vast majority of adverse events after COVID-19 vaccination are mild to moderate (grade 1 or 2), with the most common being injection site pain, fatigue, myalgia, headache, and fever 4.
There are no absolute contraindications to COVID-19 vaccination in cancer patients undergoing chemotherapy, radiotherapy, hormonal therapy, immunotherapy, or surgery 4.
Common Pitfalls to Avoid
Do not delay vaccination in cancer patients due to unfounded concerns about cancer risk—the protective benefits against COVID-19 mortality far outweigh any theoretical concerns 4, 5, 6.
Do not confuse pandemic-related diagnostic delays with actual increases in cancer incidence—the observed patterns reflect healthcare disruption, not vaccine effects 3.
Do not give equal weight to methodologically flawed studies—prioritize large-scale population surveillance data over smaller observational studies with inherent confounding 1.
Continue monitoring for immune-related adverse events (IRAEs) in the 2-3 days following vaccination in patients on checkpoint inhibitors, but recognize these are distinct from cancer development 4, 5.