Moderna’s Flu Shot Falls Short of Early Success Threshold

Pictured: Moderna logo on a white building/hapabapa/iStock

Pictured: Moderna logo on a white building/hapabapa/iStock

An interim analysis of Moderna’s Phase III P302 study showed its investigational flu shot, mRNA-1010, fell short of the statistical threshold for early success due to what the company stated was a low number of infected participants.

Moderna made the announcement in a pipeline update Tuesday.

Despite failing the interim efficacy analysis, an independent Data and Safety Monitoring Board found no safety issues with the vaccine candidate and recommended that the study continue collecting efficacy data until the next analysis.

Moderna stock was down 3.6% at market close Tuesday following the news.

Developed using the company’s proprietary mRNA platform, mRNA-1010 is Moderna’s first flu vaccine candidate. It works by encoding for hemagglutinin glycoproteins found on four influenza strains, in line with WHO recommendations: A/H1N1, A/H3N2, influenza B/Yamagata lineage and influenza B/Victoria lineage.

Moderna is currently running two Phase III trials in parallel to assess the safety and immunogenicity of mRNA-1010. The first, P301, is a randomized and observer-blinded study that enrolled more than 6,100 patients from the southern hemisphere, across sites in Argentina, Australia, Colombia, Panama and the Philippines.

Preliminary data from P301, released in February, showed mRNA-1010 resulted in better seroconversion rates for A/H1N1 and A/H3N2 strains compared with a licensed seasonal flu vaccine. Against both influenza B strains, Moderna’s investigational shot was non-inferior to the approved vaccine.

As for safety, mRNA-1010 was generally well-tolerated but led to a higher rate of solicited adverse reactions than the active comparator. Most side effects were mild.

The second study, P302, is being conducted exclusively in the northern hemisphere. During Tuesday’s data drop, Moderna posted immunogenicity data showing that mRNA-1010 elicited geometric mean titer ratios indicative of better protection against both influenza A strains. It was non-inferior against both influenza B strains. P302 had no pre-specified success criteria for immunogenicity.

An updated version of mRNA-1010, which is expected to be stronger against influenza B strains, will enter a confirmatory Phase III study later this month, Moderna announced.

Moderna’s flu vaccine pipeline also includes mRNA-1011 and mRNA-1012, penta- and hexavalent candidates that encode for more hemagglutinin candidates to target more influenza strains.

The company is also developing mRNA-1020 and mRNA-1030, both of which express neuraminidase antigens to prime the immune system against more conserved regions of the flu virus.

Tristan Manalac is an independent science writer based in metro Manila, Philippines. He can be reached at or

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