Moderna's mRNA flu vaccine clears Phase 3 with superior efficacy

Overview

For 80 years, flu vaccines grew in chicken eggs — a process effective against roughly 40% of infections in good years. On May 8, the New England Journal of Medicine published Moderna's Phase 3 data: mRNA-1010 reduced influenza illness by 26.6% more than a standard shot in 40,805 adults aged 50 and older. Moderna's stock rose 16% that day.

The standalone flu shot awaits FDA approval by August 5. Moderna's combination flu-and-COVID vaccine, mCOMBRIAX, got EU marketing authorization in April — the first single vaccine cleared anywhere against both diseases. The US hasn't approved either product.

Why it matters

If approved, an mRNA flu shot could cut hospitalizations among the 65-and-older group that suffers 70-85% of US flu deaths each year.

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Key Indicators

26.6%

Relative efficacy advantage

How much better mRNA-1010 performed than a licensed standard-dose flu shot in the trial.

40,805

Trial participants

Adults aged 50 and older across 11 countries, randomized between mRNA-1010 and a standard comparator.

Aug 5, 2026

FDA decision date

The PDUFA target by which the FDA must rule on Moderna's application.

45,000

US flu deaths in 2024-25

CDC estimate for the most recent season — a 15-year high in hospitalizations.

65.8%

Injection-site pain rate

Share of mRNA-1010 recipients reporting sore arms, versus 29.8% for the standard shot.

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People Involved

Stéphane Bancel

Pushing mRNA-1010 through a hostile US regulatory environment

Robert F. Kennedy Jr.

Cancelled federal mRNA vaccine research funding in August 2025

Vinay Prasad

Reversed the initial refusal to review mRNA-1010

Organizations Involved

Moderna

Biotechnology Company

mCOMBRIAX approved in EU (April 2026); mRNA-1010 awaiting FDA decision by August 5, 2026

Cambridge, Massachusetts biotech that produced one of the first authorized COVID-19 vaccines and is now applying mRNA technology to seasonal flu, RSV, and combination shots.

U.S. Food and Drug Administration

Federal regulatory agency

Reviewing mRNA-1010 with August 5, 2026 decision deadline

Agency that approves vaccines for the US market, including the choice of which products the federal government recommends and pays for.

Sanofi

Pharmaceutical Company

Defending Fluzone High-Dose franchise against mRNA entrants

French pharma company that sells Fluzone High-Dose, the leading enhanced flu vaccine for adults 65 and older.

Timeline

FDA decision deadline
Regulatory

PDUFA goal date by which the FDA must rule on Moderna's application.
August 5th, 2026
Moderna stock up 16%; analysts raise price targets
Market

Following the May 8 NEJM publication, Moderna shares closed 16% higher. Evercore ISI raised its price target to $50 from $35, Goldman Sachs raised its to $49 from $43, and Piper Sandler initiated coverage with a Buy rating.
7 days ago
Phase 3 efficacy data published in NEJM
Publication

The 40,805-person P304 trial shows mRNA-1010 cut influenza cases by 26.6% relative to a standard-dose vaccine, with consistent benefit across H1N1, H3N2, and B/Victoria strains.
May 8th, 2026
Moderna posts Q1 2026 earnings of $389 million
Financial

Moderna reported first-quarter revenue of $389 million, about 80% from international markets. Net loss of approximately $1.3 billion included a $900 million litigation settlement charge. Management reiterated guidance of up to 10% revenue growth for 2026.
May 1st, 2026
EU approves Moderna's flu-COVID combination vaccine
Regulatory

The European Commission granted marketing authorization for mCOMBRIAX, Moderna's mRNA vaccine against both seasonal influenza and COVID-19. It is the first single vaccine approved anywhere against both diseases, indicated for adults 50 and older.
April 22nd, 2026
ESCMID data: repeat mRNA-1010 vaccination shows no new safety signals
Clinical Trial

Moderna presented a post-hoc analysis at ESCMID Global 2026 in Munich showing sequential mRNA-1010 vaccination produced similar antibody responses regardless of prior flu vaccine type. No new safety concerns were observed with repeat dosing.
April 19th, 2026
FDA reverses the refusal
Regulatory

After a Type A meeting with Moderna, FDA accepts the mRNA-1010 application for substantive review and sets the PDUFA date.
March 1st, 2026
FDA refuses to file the application
Regulatory

CBER rejects Moderna's submission on grounds that the comparator should have been a high-dose, not standard-dose, flu vaccine.
February 12th, 2026
Reformulated vaccine hits all endpoints
Clinical Trial

P303 trial of an optimized composition shows higher antibody titers than a standard-dose comparator across all strains.
March 27th, 2024
First Phase 3 results from Southern Hemisphere
Clinical Trial

P301 trial in 6,102 adults across five countries meets immunogenicity endpoints for A strains but misses some B-strain criteria.
February 16th, 2023
Phase 1 interim data released
Clinical Trial

Moderna reports the vaccine produces antibody responses across all four influenza strains tested.
December 10th, 2021
First mRNA-1010 dose given in Phase 1
Clinical Trial

Moderna begins testing mRNA-1010 in healthy adults at doses ranging from 6.25 to 200 micrograms.
July 7th, 2021

Scenarios

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Predictions leaderboard

FDA approves mRNA-1010 for the 2026-27 flu season

FDA clears mRNA-1010 on or near August 5 for adults 50 and older. Moderna ships in time for fall vaccination drives. Insurers cover it at parity with other flu shots after ACIP recommends inclusion. First-season revenue is modest because Moderna lacks Sanofi's pharmacy distribution muscle, but mRNA-1010 establishes a beachhead in the $8 billion global flu market.

Discussed by: Moderna investor relations; analysts at Jefferies and Leerink

Consensus —

FDA approval, ACIP refuses to recommend

FDA clears the vaccine on the clinical record, but the Advisory Committee on Immunization Practices — now stacked with members appointed under HHS Secretary Kennedy — declines to add mRNA-1010 to the recommended schedule. Without ACIP recommendation, federal Vaccines for Children coverage and most state mandates do not apply. Commercial uptake stays small.

Discussed by: STAT News, CIDRAP, vaccine policy analysts at KFF

Consensus —

FDA delays decision past PDUFA date

FDA issues a Complete Response Letter or extends the review, citing the comparator-choice issue that drove the original refusal. Moderna misses the 2026-27 season entirely. The company has to either run a new head-to-head trial against Fluzone High-Dose — adding two years and several hundred million dollars — or fight the decision in court.

Discussed by: Fierce Pharma, Endpoints News

Consensus —

Combination shot leapfrogs the standalone

Moderna's mRNA-1083 COVID-flu combination clears its own regulatory path and arrives in market before standalone mRNA-1010 gains traction. The combination becomes the company's primary flu product, and mRNA-1010 functions mostly as a platform validator rather than a major revenue driver.

Discussed by: Pharmaphorum, Reuters health analysts

Consensus —

Historical Context

Fluzone High-Dose approval (2009)

December 2009

What Happened

Sanofi's high-dose flu vaccine became the first product approved for outperforming standard flu shots in older adults. A 2014 NEJM trial in 31,989 people aged 65+ found 24% better protection than the standard shot. The vaccine carried four times the antigen.

Outcome

Short Term

Adoption in adults 65 and older grew steadily, supported by ACIP's eventual preferential recommendation in 2022.

Long Term

High-dose became the de facto standard of care for older adults and now drives most of Sanofi's $3 billion-plus flu vaccine revenue.

Why It's Relevant Today

Fluzone High-Dose is the comparator FDA initially demanded Moderna use instead of standard-dose. Its commercial dominance also defines the market mRNA-1010 must crack.

COVID-19 mRNA vaccine authorization (2020)

December 2020

What Happened

FDA granted emergency use authorization to mRNA vaccines from Pfizer-BioNTech and Moderna within eleven months of the SARS-CoV-2 genome being published. The vaccines were the first mRNA products ever approved for human use. Phase 3 trials enrolled roughly 30,000 to 44,000 people each.

Outcome

Short Term

More than 670 million doses administered in the US; mRNA technology validated at scale.

Long Term

Moderna and Pfizer pivoted from one-product COVID businesses to building broader mRNA pipelines for flu, RSV, cancer, and rare disease.

Why It's Relevant Today

mRNA-1010 is the test of whether the platform works for non-pandemic, seasonal use. A flu approval would be the first step from emergency tool to routine medicine.

Cell-based flu vaccine transition (2012)

November 2012

What Happened

FDA approved Flucelvax, the first US flu vaccine grown in animal cells rather than chicken eggs. The technology avoided the egg-adaptation mutations that can reduce match between vaccine and circulating strains. Production was also faster — useful when strains shift late in the season.

Outcome

Short Term

Slow uptake against entrenched egg-based supply chains.

Long Term

Cell-based now accounts for a meaningful but minority share of US flu vaccine supply; egg-based remains dominant.

Why It's Relevant Today

Shows how hard it is to displace an 80-year-old manufacturing platform even with a clear technical advantage. mRNA-1010 faces the same incumbency problem.