Maidenhead, United Kingdom – September 16, 2026 -- CSL Seqirus has published pivotal Phase 3 results for its MF59-adjuvanted, cell-based, higher-dose quadrivalent influenza vaccine (aQIVc) in The Lancet Infectious Diseases, reporting superiority over an adjuvanted egg-based comparator across all four influenza strains and age groups tested in a 7,699-participant trial.
Trial enrolled nearly 7,700 adults aged 50 and older across eight countries
The randomised, observer-blind study recruited participants in Canada, Denmark, Estonia, Germany, Pakistan, the Philippines, the United Kingdom and the United States, comparing aQIVc against an MF59-adjuvanted egg-based quadrivalent vaccine and a recombinant quadrivalent vaccine. The vaccine met its primary objectives, showing non-inferiority versus the recombinant comparator for three of four strains in the 50-plus group and four of four strains in those aged 65 and above.
Immune responses persisted through the flu season with a mild safety profile
Researchers reported that immune responses were sustained throughout the influenza season, and most adverse reactions were mild or moderate, resolving within three days. Exploratory findings also showed enhanced neuraminidase antibody responses compared with the two comparator vaccines, an emerging marker researchers link to reduced disease severity and broader protection.
Regulators in the UK and EU have already cleared the trivalent formulation
The trivalent formulation of aQIVc, marketed as AUJEMFLU, received approval from the UK's Medicines and Healthcare products Regulatory Agency earlier in 2026 and from the European Commission for adults aged 50 and older. CSL Seqirus has filed regulatory submissions for the trivalent formulation in multiple additional markets, with a phased rollout planned according to local regulatory, policy and access pathways.
Vaccine combines three established technologies in a single dose for the first time
Each dose contains 45 micrograms of haemagglutinin per influenza strain and 19.5 mg of MF59 adjuvant, combining cell-based manufacturing, MF59 adjuvant and a higher-dose formulation — three approaches previously used separately in influenza vaccines but not evaluated together at this scale until now.
Gregg Sylvester, Chief Medical Officer and Head of Research & Development at CSL Seqirus, said the Lancet publication reflects "decades of investment in influenza vaccine innovation" and provides evidence for healthcare professionals and immunisation advisory groups evaluating future vaccination strategies for older adults.
Study authors say findings support review by national immunisation advisory bodies
The study authors concluded the data support further evaluation of the vaccine and offer evidence for National Immunisation Technical Advisory Groups weighing enhanced influenza vaccination strategies for older populations, a demographic where waning immune responsiveness continues to drive hospitalisations and deaths despite existing vaccination programmes.