FDA Approves Moderna's New mRNA Flu Vaccine Showing Improved Effectiveness
The U.S. Food and Drug Administration (FDA) has approved Moderna's new seasonal flu vaccine, Meflosiva, the first flu vaccine based on mRNA technology. This approval marks a significant advancement after decades, as the vaccine demonstrated a 26.6% higher relative efficacy compared to a standard-dose flu vaccine in a large clinical trial.
The approval was granted through two pathways: a full approval for adults aged 50 to 64 based on clinical trial safety and efficacy data, and an accelerated approval for those 65 and older, requiring Moderna to conduct further studies to confirm clinical benefits in the elderly. This is not an emergency use authorization but a marketing approval with ongoing data collection requirements.
The pivotal study involved 40,703 participants aged 50 and above, randomly assigned to receive either Meflosiva or a standard flu vaccine. Confirmed flu cases were 2% in the Meflosiva group versus 2.8% in the standard vaccine group. Meflosiva targets two influenza A strains and one influenza B strain, using mRNA molecules encased in lipid particles to instruct cells to produce viral proteins that trigger immune responses without containing live virus.
One key advantage of the mRNA platform is the potential to shorten vaccine production time from about six months to two to three months, allowing for more timely strain selection. However, it remains unproven whether this faster production will consistently translate into better clinical protection each flu season, given the frequent genetic changes in flu viruses.
Side effects were more common with Meflosiva, including injection site pain (66% versus 30%), fatigue, headaches, muscle pain, and chills, but most were mild to moderate and resolved within days. Serious adverse events were similar between groups, with no new safety concerns identified.
In Israel, the vaccine has not yet been approved. FDA approval currently applies only in the U.S., and local marketing would require separate authorization by Israel's Ministry of Health. Considerations for Israeli approval include cost, availability, strain composition for the northern hemisphere, and its role alongside existing enhanced flu vaccines for older adults.
