Senate Hearing Spotlights Unresolved Debate Over mRNA COVID Vaccines and Cancer Risk
Key Insights
Sen. Ron Johnson convened a June 3 hearing alleging mRNA COVID vaccines may cause cancer and that research on safety signals has been systematically suppressed by federal health agencies.
Witnesses including Dr. Angus Dalgleish and Dr. Wafik El-Deiry argued for scientific freedom to investigate vaccine safety concerns, while ASCO's Dr. Julie Gralow stated there is no clinical evidence linking mRNA vaccines to cancer.
Sen. Richard Blumenthal countered by citing NCI conclusions and a JAMA study of nearly 30 million people showing vaccinated individuals were less likely to die from cancer four years post-vaccination.
A contentious Senate hearing on June 3 laid bare the deep and unresolved divide over whether mRNA COVID-19 vaccines (search) can cause or accelerate cancer, as Sen. Ron Johnson (R-WI) convened a panel of doctors who argued that vaccine safety signals have been systematically suppressed by federal health agencies and scientific journals.
The hearing, titled "Plausible Mechanisms of COVID-19 (search) Injections Causing Cancer and Attacks on Scientific Publications and Research," was held before the Senate Permanent Subcommittee on Investigations and marked the third in a series Johnson has run in the 119th Congress on COVID vaccine safety. It follows an April 2025 hearing that produced an interim report titled "Unmasked: How Biden Health Officials Purposely Turned a Blind Eye Toward COVID-19 Vaccine Injury Safety Signals," and a May 2025 hearing focused on myocarditis linked to COVID vaccines.
Witnesses Present Divergent Accounts
Angus Dalgleish, Professor Emeritus of Oncology at City St. George's, University of London, delivered some of the hearing's most striking testimony, describing six of his melanoma patients who had been stable for years and then relapsed after receiving a booster vaccine. "Its use for future vaccines should be banned, and the COVID ones stopped now," Dalgleish told lawmakers.
Wafik El-Deiry, Director of the Legorreta Cancer Center at Brown University, framed the issue as one of scientific freedom: "Scientists deserve the freedom to investigate legitimate scientific concerns."
Julie Gralow, chief medical officer of the American Society of Clinical Oncology, offered the hearing's most direct defense of the scientific consensus. "There is no clinical evidence proving that mRNA COVID-19 vaccines (search) cause cancer," Gralow testified. She further noted that cancer develops over years or decades and that "the appearance of late-stage aggressive tumors within weeks or months of an injection is biologically incompatible with what we've learned from decades of research."
Sharp Exchanges Over Vaccine Mechanics
The hearing's most contentious moment came when Johnson pressed Gralow on whether she understood that the mRNA in COVID vaccines was modified with pseudouridine and was not standard mRNA. When she acknowledged uncertainty about lipid nanoparticle biodistribution, Johnson shot back: "You're saying how safe and effective this is, but you don't know how it works." Gralow responded that she does know how it works — that it incites an immune reaction — but the exchange illustrated Johnson's strategy of using technical questions to challenge the credibility of the mainstream scientific position.
Claims of Research Suppression
Several witnesses described their published research being retracted or facing institutional pushback. Sabine Hazan, CEO of ProgenaBiome (search), detailed a series of retractions, including a 2021 paper on COVID in patient feces, a 2022 paper on ivermectin-based therapy, and a 2024 paper on cardiac safety of hydroxychloroquine. She argued the retractions were politically motivated: "If there was a treatment, vaccines would not have passed."
Saskia Mostert, a Dutch researcher, described the institutional response to her team's 2024 BMJ Public Health study on excess mortality across 47 Western countries as "blind fury," and said that while the study found no plagiarism or falsification, her institution still sought retraction.
Aseem Malhotra, a British cardiologist at the HUM2N Clinic in London, described himself as "a grieving vaccine injured doctor" and accused multinational pharmaceutical corporations of meeting the criteria for psychopathy as defined by forensic psychologists.
The Counter-Narrative
Sen. Richard Blumenthal (D-CT), the ranking member, used his time to present an opposing view. He cited the National Cancer Institute's conclusion that "there is no evidence that COVID-19 (search) vaccines cause cancer, lead to recurrence, or lead to disease progression," and submitted for the record a JAMA study of nearly 30 million people finding that vaccinated individuals were less likely to die from cancer four years after vaccination.
Blumenthal also raised what he called the real threat: the Trump administration's cuts to cancer research funding. He asked Gralow directly whether cutting NIH research funding would cost lives. Her answer was unequivocal: "Absolutely."
Tamika Felder, a 25-year cervical cancer survivor and patient advocate, offered a direct counterpoint to the vaccine-skeptical witnesses, arguing that attacks on the HPV vaccine would cost lives: "No one in the United States of America should die of cervical cancer."
A Mirror-Image Controversy
The hearing unfolded against a backdrop of reported actions by the Trump administration that have complicated the political narrative. The administration has halted CDC (search) vaccine promotion campaigns, curtailed COVID vaccine recommendations through HHS, and, according to reporting by the New York Times and BMJ, blocked publication of FDA studies that supported vaccine safety. This has created a situation in which both sides are now accusing the other of suppressing science.
Johnson, in an interview following the hearing, called the government's handling of COVID-19 (search) vaccine safety signals the "biggest government scandal of my lifetime," adding: "I can't prosecute. I can't convict. But I can expose and I think that's the first line of accountability."
What Comes Next
Johnson has signaled the hearing series will continue. The subcommittee's interim report from April remains active, and the pattern of escalating hearings suggests a formal subcommittee report or legislative referral is possible. Upcoming pressure points include FDA and NIH reauthorization cycles, where the hearing record could inform appropriations riders or oversight language.
Gralow acknowledged that further research on vaccine-related cancer signals may be warranted and agreed that cancer patients would want to know if any drug or vaccine increased their risk. She also cited a Vanderbilt University study showing cancer patients who received COVID vaccines had a 50 percent reduction in hospitalization risk. But the hearing ultimately put two irreconcilable scientific narratives on the same dais, with each side accusing the other of suppressing the truth, and no resolution in sight.