GSK advances mRNA flu vaccine to late-stage trial after strong mid-stage results

On September 1, 2026, GSK announced it will advance its mRNA-based seasonal influenza vaccine candidate to a late-stage trial starting in September 2026. The candidate, which targets haemagglutinin and neuraminidase surface proteins to improve protection and reduce transmission, showed stronger mid-stage immune responses than standard- and high-dose shots. This trial is part of GSK's broader push under CEO Luke Miels to launch 25 late-stage studies by late 2026 to counter looming patent cliffs, following Moderna's August 2026 FDA approval of its mFlusiva mRNA flu vaccine.

GSK mRNA flu vaccine trial

• ▪GSK intends to begin the late-stage trial for its mRNA-based seasonal influenza vaccine candidate in September 2026
• ▪GSK announced on September 1, 2026, that it will advance its mRNA-based seasonal influenza vaccine candidate to a late-stage trial

Dual-protein targeting approach

• ▪GSK's late-stage trial will be the first of an mRNA flu vaccine designed to target two key surface proteins, haemagglutinin and neuraminidase
• ▪GSK stated that targeting both haemagglutinin and neuraminidase surface proteins could improve protection against seasonal influenza and reduce transmission

Mid-stage immune response results

• ▪Mid-stage data showed GSK's mRNA-based seasonal influenza vaccine candidate generated stronger immune responses than currently approved standard- and high-dose shots in younger and older adults
• ▪The decision to advance GSK's mRNA-based seasonal influenza vaccine candidate to a late-stage trial was driven by positive mid-stage immune response data

Moderna mFlusvax FDA approval

• ▪Moderna's mFlusiva mRNA-based seasonal flu vaccine was approved in the United States specifically for people aged 50 and older
• ▪In August 2026, Moderna won U.S. approval for its seasonal flu vaccine mFlusiva, which is the first mRNA-based vaccine approved for seasonal flu

GSK drug development acceleration

• ▪GSK's portfolio review by CEO Luke Miels aimed to speed up drug development ahead of looming patent cliffs
• ▪GSK plans to start 25 late-stage studies by the end of 2026 following a portfolio review by CEO Luke Miels

2 sources