Moderna’s COVID-Flu Combo Shot Beats Separate Vaccines in Phase III Study

Moderna building

Pictured: Moderna's office in Cambridge, Massachusetts/iStock, hapabapa

Moderna on Monday unveiled Phase III data for its investigational combination vaccine mRNA-1083, which demonstrated a superior immune response against COVID-19 and influenza compared to licensed vaccines.

In patients aged 65 years and older, mRNA-1083 triggered significantly higher immune responses than two co-administered licensed vaccines, which are routinely recommended—Fluzone HD, an enhanced flu vaccine, and Moderna’s COVID-19 shot Spikevax. The investigational vaccine induced a stronger response against SARS-CoV-2 and the H1N1, H3N2 and B/Victoria influenza strains.

Moderna’s experimental combo shot also elicited significantly better immune responses against these viruses in adults aged 50 through 64. In this younger age group, mRNA-1083 was compared with the co-administration of Spikevax and the standard-dose flu vaccine Fluarix.

The late-stage study found mRNA-1083 to be non-inferior to licensed comparators in both age groups against the B/Yamagata influenza strain, which has increasingly disappeared from circulation, according to Moderna.

In terms of safety, most of the adverse events associated with mRNA-1083 were grade 1 or 2 in severity. The most common side effects included headaches, fatigue and injection site pain.

“Combination vaccines have the potential to reduce the burden of respiratory viruses on health systems and pharmacies, as well as offer people more convenient vaccination options that could improve compliance and provide stronger protection from seasonal illnesses,” Moderna CEO Stéphane Bancel said in a statement.

With Monday’s readout, Moderna has become “the only company with a positive Phase III flu and COVID combination vaccine,” Bancel said. The pharma will present complete Phase III data and analyses at an upcoming medical congress and will work with regulators to determine the next steps for mRNA-1083.

MRNA-1083 combines two of Moderna’s investigational mRNA vaccines. The first is the flu vaccine candidate mRNA-1010, which encodes for the hemagglutinin glycoproteins of the H1N1, H3N2, B/Victoria and B/Yamagata influenza strains.

In February 2023, Moderna posted interim Phase III data for mRNA-1010, which was able to elicit better seroconversion rates for the H3N2 and H1N1 strains. However, the investigational shot did not meet its non-inferiority bar for seroconversion for the B/Victoria- and B/Yamagata-lineage strains.

The second component of mRNA-1083 is mRNA-1283, a next-generation COVID-19 vaccine candidate. In March 2024, Moderna announced that mRNA-1283 met its primary endpoint in a Phase III trial, eliciting a stronger immune response against SARS-CoV-2 compared with the pharma’s licensed COVID-19 vaccine. This advantage was consistent for both the Omicron BA.4/BA.5 and wildtype strains and was pronounced in older adults over 65 years of age.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at or

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