An article published in 2025 claimed a link between coronavirus vaccines and an increase in the incidence of several types of cancer, but critical examination reveals fundamental flaws: too short a follow-up period, lack of control over key risk factors, and lack of a proven biological mechanism.
Studies From Israel And the world has shown that the vaccines commonly used in the Western world against coronavirus, especially the mRNA vaccines, are very safe to use and effectively prevent infection with symptoms, severe illness requiring hospitalization, and death. Studies that summarized the findings of hundreds of previous studies (meta-analyses) conducted at different times and in different places around the world, Strengthened These findings.
In September 2025, researchers from South Korea published Article in the journal Biomarker Research, in which they claimed that there was a link between coronavirus vaccines and the development of cancer. The researchers examined the incidence of cancerous diseases in the year after vaccination and claimed that they found a link between an increase in the incidence of several types of cancer and coronavirus vaccines – mRNA vaccines and vaccines that use a genetically modified virus to bring the immune system together with parts of the real pathogen (viral vector). But just a month later, the journal's editors added a note that questions had arisen about the article and that it was under review.
More sick or more reported?
One of these questions concerns the speed with which cancer apparently developed in the study participants, since for most types of cancer, one year is not enough for a tumor to develop. For example, the papillomavirus, a known carcinogen whose mechanism of action was deciphered years ago, causes cancer to develop within an average of 15 years. Similarly, exposure to the sun during childhood leads to the development of skin cancer only decades later. Of the six types of cancer that the researchers examined – thyroid, stomach, colon, lung, breast and prostate cancer – only lung and breast cancer tend to develop within a year or less. The other types of cancer that were examined are much slower, so the vaccinated people who were diagnosed with cancer probably had the disease before the vaccine.
The study found that in men who were vaccinated against COVID-19, the incidence of lung and bowel cancer was higher than in women, and found additional correlations with age and sex – but the six types of cancer that the researchers reviewed are only the six types for which there are screening tests in South Korea. Other types of cancer were not examined. Most of the correlations found in the study also exist in the unvaccinated. For example, the researchers wrote that the risk of cancer in those vaccinated against COVID-19 increases from the age of 65 – but at this age, even those who are not vaccinated are more likely to have cancer.
The third factor
A major weakness of such studies is that they can indicate connections between phenomena, but not causation, meaning that one phenomenon causes the other. So finding a purported connection between coronavirus vaccines and cancer could indicate that the vaccine causes cancer – or that there is another, third factor from which both phenomena arise.
For example: Older people are more likely to be vaccinated than younger people, and they also have a much higher incidence of cancer. Another possible explanation is that populations that are more health-conscious are more likely to be vaccinated and also have more medical tests that can allow for early diagnosis of cancer. Another possibility is that city dwellers are more likely to be vaccinated than those in the rural periphery, and in cities there is greater exposure to carcinogens such as polluted air. Since the study did not collect data on other possible risk factors for cancer, such as smoking, dietary habits or lifestyle, it is impossible to confirm or rule out alternative explanations for the association.
This is what happened with the coronavirus pandemic: some dismissed the coronavirus as the flu, and thus many deaths from the coronavirus were attributed to other causes. In the same way, many breast cancer patients who did not get vaccinated because they were scared of vaccines were also not tested and diagnosed with cancer because they were scared of breast cancer screening. This created a false correlation according to which women who did not get vaccinated against COVID-19 also did not get breast cancer.
The study found that during the first three months after the vaccine, the rate of cancer diagnosis increased – but after a year the incidence of its diagnosis in the vaccinated population returned to being similar to the average in the general population. This finding was probably a statistical anomaly, or it was due to the fact that the vaccine recipients were confined to their homes and therefore took advantage of the time to get tested – and when more people are tested, more cancer patients are diagnosed, so this finding does not support the hypothesis that the vaccine caused the cancer. The average number of cancer cases in the study subjects was actually Lower than the national average In South Korea during the vaccination period. Also, no increase in cancer cases was observed worldwide after the vaccination campaign.
The missing mechanism
The authors of the article claimed that booster doses “significantly affected” the incidence of three types of cancer, but provided no evidence for this claim. It is not enough to prove that the incidence of cancer increased in parallel with the vaccines – which the study did not prove – it is necessary to prove that the vaccine has a mechanism of action that causes cancer, a biological mechanism by which the mRNA molecules in the vaccine – molecules that break down within hours and are washed out of the body – may cause cancer. So far, no evidence has been found for the existence of such a mechanism.
An mRNA vaccine uses the body's ability to transport lipid particles to deliver genetic material to cells. The mRNA is wrapped in a shell of tiny fats, lipids, and because the membrane, the cell membrane, is made of lipids, the lipids that surround the mRNA fuse with it. After injection into the muscle, the mRNA molecules enter nearby cells and nearby lymph nodes and are released from the shell. The ribosomes in each cell read the mRNA and produce the virus's spike protein. The protein is displayed on the membrane and the immune system recognizes it as part of the coronavirus and develops an immune response. The vaccine thus causes the cells to produce the coronavirus's spike protein, which activates the immune system.
Within hours to days – a few weeks in exceptional cases – Digestive enzymes the spike protein into building blocks that the body recycles. After a few weeks, the immune system clears the spike protein that is displayed on the cell membrane. There is reports Individual on tiny amounts of mRNA or spike protein In immune system cells A month or more after vaccination. Contrary to the claims of vaccine opponents, mRNA molecules do not enter the cell nucleus and do not change the DNA.
Vaccination actually protects against cancer
Published in December 2025study Which included almost 30 million people and examined causes of death four years after vaccination. The study found that the vaccine does not increase the risk of mortality, reduces death from corona and also reduces harm from other causes, for exampleFrom cardiac events And additional damage to the heart and blood vessels – perhaps because the virus damages the blood vessels and the immune system, and the vaccine reduces the effect of the virus.
Other studies have found no link between coronavirus vaccines and cancer, and several Studies have also found Vaccines may help treat cancer. A mechanism has been found that explains How the vaccine helps the immune system fight not only coronavirus but also cancer. A study from 2024 Find That an mRNA vaccine against coronavirus provides protection against a type of brain cancer, melanoma skin cancer, and one type of lung cancer.
Burden of proof
In conclusion, to strengthen the suspicion of a link between the mRNA vaccine against Corona and various types of cancer, it is necessary to examine the correspondence between the date of vaccination and the incidence rate of more types of cancer, for a longer period. A correlation must be proven between an increase in the rate of those vaccinated and an increase in the rate of those with cancer. The study found only a partial correlation, and even then – with the help of selective data selection.
In addition, causality must be proven – a biological mechanism by which the vaccine may accelerate cellular processes that cause cancer. The study did not establish such a mechanism, and even in the field it examined, statistics, much larger studies have been conducted and their findings contradicted its findings.
Studies have found a correlation There is a link between the coronavirus vaccine and a number of rare symptoms, including myocarditis, an inflammation of the heart muscle. However, the rate of myocarditis is between ten and twenty out of a million vaccinated people, the vast majority of whom have mild symptoms, and studies on tens of millions of people Found The risk of myocarditis is higher after contracting the coronavirus than after vaccination, sometimes up to ten times.
Follow-up studies conducted among several times larger population groups did not find the same correlations between vaccination and cancer, and did not reach the same conclusions. Follow-up studies must attempt to confirm or deny a correlation between the coronavirus vaccines and cancer, prove a causal relationship between the vaccine and cancer, and present a mechanism of action by which the vaccine causes cancer – which has not been done so far.
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