GSK moves its mRNA flu vaccine into Phase 3 trials

GSK thinks it has built a better flu shot. On September 1, the company said it will start a Phase 3 trial. That's the last major testing stage before a vaccine can seek approval. This one uses mRNA, the same vaccine technology behind the COVID shots. In an earlier trial of 971 adults, GSK's version triggered stronger immune responses than today's flu vaccines. That held true in both younger and older adults.

GSK isn't the only company chasing this. Moderna's own mRNA flu vaccine, mFlusiva, already won FDA approval earlier this year. That's exactly why GSK is racing to catch up. GSK's pitch is that its version does something Moderna's doesn't. It targets two different flu surface proteins instead of one. GSK says that could mean stronger, more complete protection. That claim hasn't been tested in a large trial yet. It's the whole reason Phase 3 exists.

Keep reading — what to watch

Will GSK's two-protein approach actually translate into a real-world edge over Moderna's shot, or fewer flu cases overall? Phase 3 trials often fail to repeat the promise of earlier, smaller studies. Respiratory virus season is approaching in the Northern Hemisphere, which is part of why GSK wants this trial running now. If the data holds up, mRNA flu vaccines could become the new standard within a few years. Right now they're just an alternative sitting next to the traditional shot.