Pfizer’s mRNA flu vaccine has outperformed the standard flu shot in a recent Phase 3 clinical trial. Findings published in the New England Journal of Medicine indicate that the mRNA vaccine exhibited a significant advantage over traditional vaccines, which have struggled with effectiveness due to strain mismatches. This development may mark a pivotal moment in influenza prevention strategies.
The trial involved over 18,000 adults primarily in the United States, with additional sites in South Africa and the Philippines. Participants received either Pfizer’s mRNA vaccine or Fluzone, one of the most widely used seasonal flu vaccines in the U.S., during the 2022-2023 flu season. Results revealed that the mRNA vaccine reduced flu-like illnesses by 34.5%, with 57 cases reported in the mRNA group compared to 87 cases in the Fluzone group.
Potential Impact and Challenges Ahead
Experts have noted that the mRNA technology, which has previously been utilized in Pfizer’s COVID-19 vaccine, could provide a more tailored response to circulating flu strains. Dr. Buddy Creech, a pediatric infectious disease physician at Vanderbilt University Medical Center, emphasized that the mRNA vaccine could be “a game-changer,” allowing for adjustments to be made closer to flu season, thus enhancing effectiveness.
Despite the promising results, Pfizer faces challenges in bringing the mRNA flu vaccine to market. Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, pointed out that there is considerable skepticism regarding mRNA vaccines, particularly from individuals like Health Secretary Robert F. Kennedy Jr., who has expressed concerns about their safety. Several states have proposed legislation to ban mRNA vaccines, complicating the approval process.
Pfizer’s Dr. Kelly Lindert, vice president of clinical research and development, stated that the company is currently in discussions with health authorities regarding the licensure of mRNA influenza vaccines. However, no specific timeline for submission or approval has been announced.
Trial Findings and Side Effects
The trial results showed that Pfizer’s vaccine provided protection against two prevalent influenza A strains: H3N2 and H1N1, as well as two influenza B strains, the Victoria and Yamagata strains. Notably, the Yamagata strain has been absent during the COVID-19 pandemic.
Both vaccines resulted in side effects such as arm pain and fatigue, although these were more frequently reported in individuals who received the mRNA vaccine. Approximately 5.6% of participants who received the mRNA shot experienced fevers, compared to 1.7% in the traditional vaccine group. Most side effects were mild to moderate and resolved within one to two days.
Creech remarked that the stronger immune response generated by the mRNA vaccine may explain the increased incidence of side effects. He likened the experience to training for a race, suggesting that some discomfort during preparation can lead to better performance during the actual event.
Meanwhile, Moderna is also developing a stand-alone mRNA flu vaccine. In June, the company announced findings indicating that its mRNA flu shot was approximately 27% more effective than an approved flu vaccine produced by GSK. Moderna plans to file for approval of its vaccine by January 2026.
As the landscape of influenza vaccination evolves, the introduction of mRNA technology could reshape public health strategies. The outcomes of Pfizer’s trial present a promising avenue for improving flu vaccine efficacy, though regulatory hurdles and public perception remain significant challenges.
