Ron Johnson

Sen. Ron Johnson held a hearing to explore the unsupported theory linking COVID-19 vaccines to cancer.

Medical experts and the National Cancer Institute state there is no evidence that COVID-19 vaccines cause cancer.

While rare, serious health issues have been recorded following vaccination, but billions of doses have been administered worldwide.

Oncologists often recommend the vaccine to cancer patients, who are at a higher risk for serious complications from the virus.

U.S. Sen. Ron Johnson said the unsupported idea that there is a link between COVID-19 vaccines and cancer "needs to be given serious consideration and study" following a hearing he held featuring researchers who have explored the idea.

Johnson has long pursued the theory that government officials and the medical field are dismissing or concealing injuries he believes were caused by the COVID-19 vaccine and has used his position as chair of the Senate's Permanent Subcommittee on Investigations to air that theory. He has held five hearings since May 2025 on the COVID-19 pandemic, vaccines and what he describes as the corruption of science.

Medical experts say that while serious health issues have been recorded following vaccination, they are rare among the billions of doses administered worldwide. Leading oncologists and the National Cancer Institute say there is no evidence that COVID-19 vaccination causes cancer or causes it to recur.

Johnson's June 3 hearing focused largely on what he called the torment of scientists who have promoted alternative treatments to COVID-19 and questioned the Pfizer and Moderna vaccines, which use mRNA technology to prompt a bodily response to fight the virus.

"The prime objective of that hearing was making people aware of the fact that science and peer review is not pure," Johnson said in an interview with the Journal Sentinel.

One witness, Dr. Wafik El-Deiry, who directs the Legorreta Cancer Center at Brown University, discussed a review he authored that examined case reports of cancers appearing after COVID-19 vaccination and COVID-19 infection.

Conclusions of a cancer link, he said in a LinkedIn post last year, "would be premature without more studies." El-Deiry said he came under fire for publishing the review.

Cancer patients face a higher risk of COVID complications

The review was "reasonably cautious" in pointing out an observation and suggesting follow-up studies, said Dr. Walter Stadler, an oncologist and chief clinical officer at City of Hope Cancer Center Chicago.

"Ongoing monitoring of the risks of cancer with things like vaccines is perfectly rational and reasonable," Stadler said in an interview. "To date, to my knowledge, there's been no good clinical or epidemiological evidence that these vaccines can cause and increase the risk of cancer. We know other risks, but not cancer."

Stadler, who treats kidney, prostate and other cancers, said he recommends the COVID-19 vaccine to his patients because they are at higher risk for serious complications from the virus.

Cancer treatments can weaken the body's ability to fight infections. A 2022 paper authored in part by UW-Madison researchers found that cancer patients who contracted COVID-19 were significantly more likely to die or be admitted to the ICU than those without a cancer diagnosis.

Studies have suggested COVID-19 mRNA vaccines stimulate the immune system to fight cancer, though Stadler cautioned that those, too, are based on case reports and there could be other reasons those patients' immune systems responded the way they did.

Every vaccine carries risks and benefits, Stadler said.

"Should we just ignore the risks and pooh-pooh them? No. But we need to discuss the risks that have been demonstrated," he said. "I'm not going to be beholden to theoretical risks."

Johnson says people want to move on, but attention on vaccine injury is 'absolutely necessary'

In a 2023 radio interview after he was re-elected to the Senate, Johnson said the reason he ran again was no one else was advocating for the vaccine-injured.

In a June 10 interview, he told the Journal Sentinel that people, likely including his Senate colleagues, "just want to move on."

But he said he's concerned that people who believe they were injured by the COVID-19 vaccine are at a "low point psychologically" and can't get honest treatment because doctors deny the root cause of their condition. He said his primary goal on the subject is to return integrity to science.

"My goal is to get people to open up their eyes and look at this honestly, as opposed to the way it's looked at right now," Johnson said.

Elisabeth Marnik, a science communicator and immunologist who is executive director of The Evidence Collective, which aims to provide Americans with health information they can trust, said in an interview that it's critical people aren't dismissed for real health problems, regardless of the cause.

She acknowledged it's difficult for people to navigate the current landscape in which trust in institutions is declining and skepticism of pharmaceutical companies is sometimes justified, pointing to the nation's opioid crisis as an example.

Still, when it comes to vaccines, Marnik said, "two things can be true at one time. We have to hold space for the fact that, yes, sometimes, there can be rare vaccine side effects. In general, there can be rare side effects to anything we do in life ... that doesn't negate the population benefit of vaccines that we have very robust data for."

She said if people encounter information about vaccines that seems scary or stressful, they should try to find other sources of information to verify it. Stadler recommended asking a primary care physician.