November 25, 2025
Pfizer reported that its mRNA flu shot outperformed conventional flu vaccines in a Phase 3 trial, but independent experts told The Defender the company’s study overstates the benefits and downplays safety signals. They cited flaws in the Pfizer-funded research, including missing data that call into question the trial’s conclusions.
Pfizer said its mRNA flu vaccine outperformed conventional flu vaccines in a Phase 3 clinical trial. The New England Journal of Medicine (NEJM) last week published the results of the study, which Pfizer funded.
The vaccine delivered “statistically superior efficacy” compared to the conventional shot, and the trial demonstrated an “acceptable safety profile,” Pfizer said.
However, some experts said the results showed a higher rate of adverse events among the group that received the mRNA vaccine compared with the placebo group.
Other critics pointed out flaws in Pfizer’s trial, and some suggested that the mRNA vaccine technology itself is unsafe.
Daniel O’Connor, editor of TrialSite News, said Pfizer’s trial showed that the mRNA flu vaccine can reduce influenza A infections, but “the benefits are modest.”
Karl Jablonowski, Ph.D., senior research scientist for Children’s Health Defense (CHD), said the results of Pfizer’s study are “invalid,” because the vaccine wasn’t tested against an unvaccinated control group.
“There is no placebo group, which means the entire claim to efficacy is based on its relative efficacy to the available flu vaccine at the time,” Jablonowski said.
Karina Acevedo Whitehouse, Ph.D., professor of microbiology at the Autonomous University of Querétaro in Mexico, said this limitation means the “study has very little scientific and medical value, despite the hype.”
“By comparing to a vaccine that is already in use, the true rate of adverse effects is underestimated,” Whitehouse said. “This approach does not allow for the evaluation of the efficacy of the mRNA vaccine and even less of the adverse events as compared to a placebo.”
Dr. Clayton Baker, an internal medicine physician, said it would have been “simple and easy — not to mention scientifically rigorous and ethically sound — for the study to have included a true placebo group.”
Jablonowski said the few studies that compare recipients of flu shots with unvaccinated subjects raise serious questions about the vaccine’s safety and effectiveness.
He cited a Cleveland Clinic study published in April that found people who got the flu vaccine were 27% more likely to get the flu than those who didn’t.
‘I do not trust them to conduct honest studies’
In conjunction with Pfizer’s study results, the NEJM published an editorial that highlighted another flaw in the study: Pfizer’s researchers didn’t include adults ages 65 and older — the group with “the highest risk of hospitalization or death” from the flu.
Whitehouse also questioned Pfizer’s track record — and its clinical trial data. “There is an obvious conflict of interest when a clinical trial is designed and conducted by the pharmaceutical company that produces the vaccine and that is set to gain enormously from its sale.”
Baker noted that, since 2000, Pfizer and its subsidiary companies “have been found guilty of 107 criminal offenses, totaling a staggering $11,261,560,400 in penalties.”
“Pfizer has been found guilty of defrauding the government an astonishing 22 times in the last 25 years. I do not trust them to conduct honest studies, nor should anyone else,” Baker said.
Pfizer’s mRNA flu shot led to higher rate of serious adverse events
In its study, Pfizer found that the mRNA flu vaccine was “associated with more reactogenicity events” — or side effects — than the conventional flu shot, although the researchers said most were “mild to moderate.”
According to the study, “Adverse events that were considered by the investigator to be related to the vaccine were reported in 3.3% of modRNA [mRNA] recipients and in 1.4% of control recipients.”
Significantly more participants who received the mRNA shot experienced redness, swelling or pain at the injection site, or developed a fever, headache, fatigue, chills, vomiting, diarrhea, muscle pain or joint pain, compared to those who received the conventional flu shot, the researchers said.
However, they reported that serious adverse events “were low and similar in the two trial groups.” One mRNA vaccine recipient developed anaphylaxis and other serious adverse events that a study investigator determined were vaccine-related.
The researchers said there were no reports of myocarditis or pericarditis — conditions widely associated with the mRNA COVID-19 vaccines.
Trial participants consisted of 18,000 healthy adults ages 18 to 64. Researchers reported that 16 participants died during the trial, but they said the deaths were unrelated to either the conventional flu vaccine or Pfizer’s mRNA flu shot.
Baker questioned that claim. “It is noteworthy that every single side effect measured in the Pfizer study was more prevalent in the mRNA group than in the traditional vaccine group,” Baker said. “Yet, the study group describes the side effects as ‘similar’ between the two groups.”
Whitehouse said the higher rate of adverse events within the mRNA group “reinforces the growing evidence that the modRNA technology can cause a myriad of cellular and molecular problems.”
French scientist Helene Banoun, Ph.D. noted the study recorded only those flu cases that began at least 14 days after injection, while infections before that were not taken into account. “Eight days after vaccination, there were already 25 cases of influenza” that were not taken into account, she said.
Data omitted from the study may have indicated an even higher incidence of serious adverse events, Jablonowski said.
“The clinical trial that forms the basis of this study actually includes 65+ individuals, though this publication omits them. That portion of the study accounts for the largest discrepancy of adverse events, as the mRNA group suffered a 7% elevated all-cause mortality … 8% elevation in serious adverse events … and an astounding 80% elevation in non-serious adverse events,” Jablonowski said.
Do we really need a flu vaccine?
The Center for Infectious Disease Research and Policy (CIDRAP) said development of a “universal” flu vaccine, effective against all flu strains, would be “The Holy Grail of flu vaccines,” but progress “has been slow going.”
According to CIDRAP, the rapid mutations of the flu virus and the slow process of developing conventional flu shots, which takes approximately six months and requires that they be ready several months before the start of the next cold and flu season, have contributed to wide variations in flu vaccine efficacy.
“Flu viruses are infamous for their ability to evolve quickly and without warning, creating a mismatch between the shots already on the market and the viral strains spreading from person to person,” CIDRAP reported.
Development of an mRNA flu shot would overcome this issue, as mRNA technology allows for the rapid development and deployment of vaccines, CIDRAP reported.
But Baker questioned the need for any flu vaccines.
“Influenza is a simple, single-stranded RNA virus. It mutates very rapidly. It is a fundamentally poor candidate for vaccines because of this,” he said. “The production method of the vaccine changes none of these basic facts about the virus itself. Vaccinating against it remains a fool’s errand.”
Whitehouse said annual flu shots strain the immune system, making them less effective. Getting repeated, annual flu vaccines can “prime and overwork the immune system,” she said, which can make the body less able to fight off a flu virus.
One of the researchers involved in Pfizer’s mRNA flu vaccine trial — Dr. Lisa A. Jackson, with Kaiser Permanente Washington Health Research Institute — previously questioned the efficacy of flu vaccines and studies claiming benefits.
Jackson co-authored a 2007 study, published in The Lancet Infectious Diseases, that cited an “evidence base” that is “currently insufficient to indicate the magnitude of the mortality benefit, if any, that elderly people derive from the vaccination programme.”
mRNA vaccine technology caused “unprecedented” health problems globally following the rollout of the mRNA COVID-19 vaccines, Whitehouse said. She cited studies showing mRNA vaccines “decrease the optimal functioning of the immune system” and cause “lymphocyte exhaustion.”
Jessica Rose, Ph.D., suggested the development of mRNA shots has more to do with the more lucrative “profit model” associated with the vaccines.
Whitehouse agreed. “What their production would ‘solve’ is the high cost of traditional vaccine production,” she said. “Manufacturing modRNA vaccines is substantially cheaper than manufacturing attenuated or live vaccines, as the latter require viral culture (in eggs) or cell culture.”
O’Connor said mRNA technology “still has unanswered questions regarding durability and frankly, long-term safety.” He said we need “far more multi-season data before calling this a meaningful advance in influenza prevention.”
In May, COVID-19 vaccine manufacturer Moderna withdrew its application for U.S. Food and Drug Administration (FDA) approval of a combination flu and COVID-19 vaccine, after the FDA requested more clinical trials.
In August, the U.S. Department of Health and Human Services (HHS) cancelled nearly $500 million in funding for mRNA vaccine research.
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Via https://childrenshealthdefense.org/defender/pfizer-claims-victory-mrna-flu-shot-critics-flaws-safety-signals/
(Photo credit: Yoan Valat/Pool via Reuters)
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