Relative efficacy vs best standard flu shot
26.6% better (95% CI: 16.7 to 35.4)
Phase 3 trial participants across 11 countries
40,805 adults
Time to update a traditional egg-based flu vaccine
up to 6 months
Time to update an mRNA flu vaccine
as little as 6 weeks
Americans hospitalised by flu in the 2024-25 season
at least 600,000
VRBPAC advisory vote to recommend approval (June 2026)
unanimous
Approval status for ages 50 to 64
standard approval
Approval status for ages 65 and older
accelerated approval
How mRNA Flu Vaccines Work
Traditional flu shots are made by growing influenza virus inside fertilised hens' eggs, then killing it, purifying the proteins, and formulating the dose. The process takes up to six months, which means health authorities must guess in February which strains will circulate the following winter. When they guess wrong, seasonal protection can drop to as low as 20%. mFlusiva skips the eggs entirely. Scientists take the genetic sequence of the target flu strains, encode the relevant surface proteins as mRNA strands, and wrap them in lipid nanoparticles, the same delivery system used in COVID-19 vaccines. Injected into your arm, the mRNA tells your cells to briefly produce flu proteins. Your immune system recognises them, builds antibodies, and destroys the mRNA within days. No live virus ever enters the equation. Speed is the defining advantage. If a new strain emerges mid-season, an mRNA update could be ready in weeks rather than the following year.
From trial to approval: the turbulent road to mFlusiva
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"This is an important advance. Influenza remains a serious public health challenge, and better vaccines mean fewer hospitalisations and deaths each year.
"Dr. Peter Marks · FDA Center for Biologics Evaluation and Research
Will mFlusiva change how you think about the annual flu shot?
The political storm around this approval was louder than the science. A vaccine with a 27% efficacy advantage survived a politicised FDA refusal, a hostile HHS secretary, and a frozen advisory committee. Does that story make you more or less likely to get it this autumn?
subtitle: Who can get mFlusiva in autumn 2026?
- Adults 50 to 64: fully approved. Standard coverage expected from most insurers once ACIP issues its recommendation.
- Adults 65 and older: accelerated approval. Confirmatory trial vs high-dose comparator required; ACIP recommendation pending court ruling.
- Under 50: not yet approved. Clinical trials in younger adults are ongoing; a broader age-group submission is planned.
- High-risk under-50s (asthma, heart disease, diabetes): mFlusiva is not yet authorised for this group. Standard options remain available.
- Already vaccinated with a standard flu shot this season: no need to switch. mFlusiva launches for the 2026-27 season.
What happens next. Moderna expects mFlusiva to be available for the 2026-27 respiratory season. The bigger bottleneck is ACIP: without a formal CDC recommendation, most insurance plans are not required to cover the shot at no cost. A First Circuit ruling on Kennedy's committee terminations could unlock that pathway. Separately, Moderna is developing a combined mRNA vaccine covering flu and COVID-19 in one injection, with a regulatory submission planned for 2027.
