GSK’s seasonal, mRNA-based influenza vaccine is progressing to a Phase III study after securing a safety and efficacy win in a mid-stage trial – potentially poising it to become a market competitor to Moderna’s newly approved mRNA shot, mFlusvia.
The British pharma company is opting to progress its candidate based on the positive results of the Flu-028 study (NCT07204964) presented at the OPTIONS XIII Conference for the Control of Influenza, taking place from 30 August 2 to September in Washington DC, in which recipients given GSK’s multivalent jab experienced higher immune responses than those given the marketed comparator standard and high-dose flu shots. The experimental vaccine also maintained an “acceptable” safety and short-term inflammatory response profile, GSK claims.
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During the Phase IIa trial, GSK randomised 971 adult volunteers to receive varying dose levels and forms of its experimental vaccine or a choice of marketed comparators – including a standard and high-dose shot. Individuals recruited to this study received varying doses depending on their age, with participants split into younger (18-64) and older (65-plus) age categories.
With these positive efficacy results in hand and a grip established on which tested vaccine configuration should move forward, GSK will progress an optimised B-strain haemagglutinin (HA) form of its vaccine to Phase III. The company hopes this trial will begin in September 2026.
Pioneering the next generation of seasonal flu vaccines
Upon the initiation of GSK’s Phase III trial, it will become the first to evaluate an mRNA-based flu vaccine targeting both HA and neuraminidase (NA) in the late-stages. According to Sanjay Gurunathan, GSK’s head of vaccines and infectious disease R&D, this approach could help to “better protect people from flu” due to its capacity to target two primary flu surface proteins, which both play a key role in the virus’ ability to bind and enter host cells.
New preventative options for seasonal flu could be particularly beneficial for public health as an estimated one billion cases and 650,000 deaths globally are linked to the virus each year.
If GSK’s vaccine reaches the market, it will come into direct competition with Moderna’s newly approved, mRNA-based seasonal flu shot, mFlusvia, which secured the US Food and Drug Administration’s (FDA) blessing in August 2026. mFlusvia obtained the regulatory greenlight at the end of a tumultuous regulatory road defined by the FDA’s initial refusal to review the vaccine entirely.
According to a sales and consensus forecast from GlobalData, parent company of Clinical Trials Arena, mFlusvia will make $831m in 2032.
Is mRNA back in the limelight?
While many researchers and drugmakers have touted the potential of mRNA-based vaccines and medicines for treating and preventing everything from infectious diseases to cancer, notably its use in the Covid-19 pandemic, the modality has been under significant scrutiny from the Trump administration – particularly from the US Health Secretary, Robert F Kennedy Jr (RFK Jr) who has long questioned its safety.
After RFK Jr publicly cut government funding to 22 mRNA vaccine development initiatives worth $500m back in August 2025, private equity financing focused on the modality also dried up in 2025 – declining 82% compared to 2023.
However, the Moderna’s landmark Phase III melanoma success for its mRNA-based cancer vaccine, intismeran autogene, has piqued analyst interest due to its potential to offer additive efficacy in the adjuvant setting over SoC Keytruda (pembrolizumab) alone. This, some say, could reignite interest in the modality despite political challenges.
However, Jefferies senior equity research analyst, Andrew Tsai, previously told Pharmaceutical Technology, sister publication to Clinical Trials Arena, that investors were unlikely to immediately flock back to placing capital in mRNA-based therapies in a hurry – with their long-term interest likely hinging on the drug class’s success in a broad range of solid tumours.
