GSK to launch Phase 3 trial for mRNA-based flu vaccine amid resurgence for the modality

News Drug Development GSK to launch Phase 3 trial for mRNA-based flu vaccine amid resurgence for the modality September 1, 2026 | 1 min read | Heather McKenzie Twitter LinkedIn Facebook Email Print GSK’s vaccine—which targets two primary flu antigens—elicited higher immune responses in both younger and older adults in a mid-stage study. The Phase 3 launch, planned for September, follows the FDA’s recent approval for Moderna’s mRNA flu vaccine. Moderna may soon have company in the mRNA flu market after GSK reported superior immune responses for its vaccine candidate in a mid-stage trial.

The U.K. pharma plans to kick off a late-stage test later this month.The Phase 2 trial compared GSK’s investigational mRNA-based vaccine to licensed inactivated flu vaccines in 971 adults, with younger adults in the control group receiving standard doses while older adults received high dose shots. Higher immune responses were seen in study participants who received GSK’s vaccine than in those receiving the existing immunizations, according to a Tuesday press release.

The investigational jab was also “generally well tolerated,” GSK said. The results were presented at the OPTIONS XIII Conference for the Control of Influenza.There is plenty of reason for GSK to be optimistic in this space. Last month, the FDA greenlit Moderna’s mFLUVISA as the U.S.’ first mRNA-based flu vaccine.

The approval came six months after the regulator refused to even review the vaccine—potentially indicating a thawing in perception around mRNA.Two weeks after the historic approval, Moderna followed up by announcing positive Phase 3 data for its Merck-partnered mRNA cancer vaccine. Approvals Moderna’s flu shot crosses FDA finish line, bouncing back from regulatory roadblock The FDA in February slapped Moderna’s vaccine with a refusal-to-file letter—though the agency backtracked a few days later and accepted a revised submission for review. An advisory committee in June unanimously backed mFLUVISA’s approval.

August 6, 2026 · 2 min read · Tristan Manalac Read more There continues to be considerable unmet need in influenza, with 1 billion global cases of seasonal flu each year and up to 650,000 respiratory deaths, per GSK. Efficacy of the currently approved flu vaccines varies, but last year’s version was only 36% effective, according to the CDC.GSK’s Phase 3 trial will be the first of its kind to test a flu vaccine targeting both haemagglutinin (HA) and neuraminidase (NA), which are “the primary surface antigens that cause the flu virus to bind and spread,” according to GSK. Currently licensed vaccines primarily target HA, the company said, adding that “growing evidence suggests [also targeting NA] could help improve protection, illness severity and transmission.”GSK’s candidate was awarded the FDA’s Fast Track designation in July.The planned Phase 3 trial will also contribute toward GSK’s goal to start more than 20 late-stage trials by the end of this year—more than double the British pharma’s previous target of 10, according to a July 28 report by Reuters, which noted that seven experimental medicines will be trialed across 18 indications.

Twitter LinkedIn Facebook Email Print Clinical research Phase 2 Phase 3 Vaccines mRNA Heather McKenzie Heather McKenzie is senior editor at BioSpace and curator of the ClinicaSpace newsletter. She is an award-winning journalist specializing in rare disease and neuroscience, in addition to her extensive coverage of the FDA and regulatory science. You can reach her at heather.mckenzie@biospace.com.

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