Pfizer‘s mRNA Flu Shot Shows Significant Advantage Over Traditional Vaccine in Trial Results
new York, NY – A late-stage clinical trial funded by Pfizer demonstrates its mRNA-based influenza vaccine is more effective at preventing flu-like illness than the widely used Fluzone vaccine, results released today show.The findings offer a potential leap forward in seasonal flu prevention as researchers continue to explore the benefits of mRNA technology beyond COVID-19.
The trial, involving over 18,000 adults primarily in the U.S., with additional sites in South Africa and the Philippines, assessed the efficacy of Pfizer’s mRNA shot during the 2022-2023 flu season. Data revealed Pfizer’s vaccine reduced flu-like illnesses by 34.5% compared to Fluzone – 57 cases in the mRNA group versus 87 cases in the Fluzone group. Protection was observed against common influenza A strains (H3N2 and H1N1) and influenza B strains (Victoria and Yamagata). Notably, the Yamagata strain has seen reduced circulation since the onset of the COVID-19 pandemic.
While both vaccines caused side effects like arm pain and fatigue, these were reported more frequently with the mRNA vaccine. Specifically, 5.6% of those receiving the Pfizer shot reported fevers, compared to 1.7% in the Fluzone group. However, most side effects were mild to moderate and resolved within one to two days.
“In some ways, this is like training for a race,” explained Dr. Creech, commenting on the increased side effects. ”We may have a little bit of muscle soreness or fatigue after a training run, but by having a little bit of discomfort then, we can avoid overwhelming fatigue or soreness during the race.”
Pfizer’s Vice President of Clinical Research and Development, Dr. Kelly Lindert,stated in an email that the company “is in discussion with health authorities on the path to licensure of mRNA influenza vaccines,” but declined to provide a timeline for submission or approval. Lindert also noted that the observed side effects could be linked to “the cascade of events from the activation of the immune response,” adding that “the relationship between side effects and immune responses is the source of ongoing discussion in the scientific community.”
Meanwhile, moderna is also developing a stand-alone mRNA flu vaccine. In June, the company reported its vaccine was approximately 27% more effective than a GSK-manufactured flu shot in a late-stage trial involving older adults, with side effects comparable to existing vaccines. Moderna plans to submit its vaccine for approval by January 2026, according to a company statement.
Dr. Peter Hotez expressed concern regarding the current department of Health and Human Services (DHHS), stating, “I’m concerned that our current DHHS has no or little interest in the science.” The DHHS did not respond to a request for comment.
Dr. Creech also emphasized that mRNA vaccines are not uniform, explaining, “not all mRNA vaccines are created the same,” and that differing efficacy levels and side effect profiles between Pfizer’s and Moderna’s shots are not unexpected.
