A new scientific study has stirred controversy by suggesting that COVID-19 vaccines may be linked to an increased risk of certain cancers. The findings, published this week in a peer-reviewed medical journal, have reignited discussions about vaccine safety and the importance of long-term monitoring. However, many medical experts are urging people not to panic, warning that the data does not prove the vaccines cause cancer.
The Study That Started the Debate
The research, published on PubMed Central (PMC), analyzed health data of thousands of individuals who received different types of COVID-19 vaccines between 2021 and 2024. The scientists compared one-year cancer risks between vaccinated and unvaccinated groups.
The authors reported what they called “potential signals”—small increases in certain cancers among vaccinated people.
Their main findings included:
- Recipients of cDNA vaccines showed higher risks for thyroid, gastric, colorectal, lung, and prostate cancers.
- People who received mRNA vaccines appeared to have a slightly higher incidence of thyroid, colorectal, lung, and breast cancers.
- Younger individuals (under 65) showed more cases of thyroid and breast cancers.
- Older adults (over 75) appeared to have an increased risk of prostate cancer.
A related Italian cohort study, published in 2025 (PMC12381369), found similar results. Vaccinated participants had a 23 percent higher rate of hospitalization for cancer within a year. However, when researchers adjusted their analysis by adding a 12-month lag period, the supposed risk disappeared. This means the link may not be directly caused by vaccination itself.
The study authors emphasized that these are early observations that require confirmation through long-term follow-up. They also warned against drawing strong conclusions from short-term data.
Why Experts Urge Caution
While the findings have generated global headlines, public-health experts and oncologists stress that the results do not prove causation. In other words, even if there’s a statistical association, it doesn’t mean the vaccine directly caused cancer.
Dr. Andrea Martelli, an oncologist at Milan University Hospital, explained:
“These signals are worth studying, but correlation is not causation. Many factors can influence cancer risk — lifestyle, genetics, infections, or healthcare access. The study does not show a biological mechanism linking vaccines to cancer.”
Experts also point out that cancers usually develop slowly over several years. Therefore, it’s unlikely that vaccination alone would lead to new cancers appearing within months.
Another concern is data bias. People who visit hospitals more often (for example, older or chronically ill individuals) are more likely to be diagnosed with cancer simply because they’re screened more frequently. This can create the illusion of higher cancer rates among vaccinated groups.
What the Broader Evidence Says
Global health authorities, including the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC), continue to affirm that COVID-19 vaccines are safe and effective. So far, there is no verified evidence that vaccines cause or accelerate cancer.
The American Cancer Society also states that “there is no evidence that any COVID-19 vaccine causes cancer or increases recurrence risk in cancer survivors.”
(cancer.org)
Several fact-checking organizations, including Reuters and Contagion Live, have debunked online claims about “turbo cancers” or sudden cancer spikes after vaccination.
(reuters.com)
(contagionlive.com)
Understanding the Possible Link
Some scientists argue that the immune system changes caused by vaccination could, in theory, influence cancer development in rare cases—but there is no consistent data to support that yet. In fact, many cancer researchers believe vaccines might reduce long-term cancer risk indirectly by preventing severe infections that weaken the immune system.
For instance, studies show that cancer patients who contract COVID-19 face higher death rates, and vaccines significantly reduce that risk.
(cidrap.umn.edu)
What Should the Public Do?
If you are concerned about this new study, experts recommend staying informed but calm. Here’s what doctors suggest:
- Don’t stop vaccinating based on early findings. The benefits of COVID-19 vaccination—including protection from severe illness, hospitalization, and death—far outweigh unproven cancer risks.
- Continue regular cancer screenings. Early detection remains the most powerful way to reduce cancer mortality, regardless of vaccine status.
- Talk to your doctor. If you have a personal or family history of cancer, your healthcare provider can explain whether this research affects you.
- Stay alert but skeptical. Many misinformation campaigns online use partial data or false claims to discourage vaccination. Always verify information from trusted health sources.
Calls for More Research
Even though the findings remain uncertain, most experts agree that continued vaccine safety monitoring is essential. Researchers are now calling for:
- Long-term tracking of cancer incidence through national cancer registries.
- Studies comparing different vaccine types (mRNA, cDNA, adenovirus, etc.) over several years.
- Transparent data sharing between governments and research institutions to improve public trust.
- Better public communication to prevent unnecessary fear or confusion.
The Ongoing Search for Answers
The 2025 study linking COVID-19 vaccines to cancer risk has opened a new chapter in the ongoing debate about vaccine safety. While it raises important questions, the evidence so far does not show that vaccines cause cancer. Most scientists emphasize that these vaccines have saved millions of lives and remain one of the safest tools in modern medicine.
As more long-term data becomes available, researchers hope to provide clearer answers. Until then, experts urge people to continue following medical guidance, stay updated on reliable research, and avoid misinformation spreading online.
