GSK announced Friday it had begun a Phase III efficacy trial of its mRNA influenza vaccine, the first candidate from the company designed to target both the haemagglutinin (HA) and neuraminidase (NA) surface proteins of the virus. The London-based drugmaker said dosing had started ahead of the Northern Hemisphere flu season.

The trial marks a strategic escalation in the race to bring mRNA technology to seasonal influenza, a market long dominated by egg-based and recombinant vaccines. GSK said adding NA as a second target could broaden protection and reduce disease severity, addressing a limitation of conventional shots that focus primarily on HA.

According to GSK, the study will enrol adults across multiple sites and measure laboratory-confirmed influenza as its primary endpoint. The company is competing with Moderna and Pfizer, both of which have advanced their own mRNA flu programmes, with Moderna having reported positive late-stage data for its candidate.

Analysts at firms including Jefferies have said an effective dual-antigen mRNA flu vaccine could reshape a global market worth several billion dollars annually and open the door to combination shots pairing influenza and COVID-19 antigens. GSK has signalled that respiratory vaccines remain central to its growth strategy.

The results, expected after the 2026-27 flu season, will help determine whether mRNA platforms can outperform established influenza vaccines on efficacy rather than merely on manufacturing speed.