Moderna's mRNA Flu Vaccine Beats Standard Shot in Late-Stage Trial

• The vaccine exceeded its primary goal of non-inferiority, proving 26.6% more effective than GSK's standard-dose flu shot in preventing influenza
• Side effects like injection-site pain, fatigue, and headache were more common with Moderna's shot but mostly mild to moderate; severe side effects occurred at similar rates (2.2% vs 1.9%)
• FDA initially rejected the application in February, arguing the company should have compared against high-dose vaccines for adults 65+, but later accepted an amended application requiring post-approval studies

Moderna's mRNA Flu Vaccine Outperforms Conventional Shot in Late-Stage Trial

Moderna's mRNA-based seasonal flu vaccine demonstrated superior efficacy compared to standard flu shots in a late-stage international trial involving over 40,000 adults aged 50 and older, according to results published in the New England Journal of Medicine.

Key Performance Data:

The Moderna vaccine (mRNA-1010) proved 26.6% more effective than GSK's approved standard-dose flu shot, exceeding the trial's primary objective of non-inferiority. This would make it the first mRNA-based seasonal flu vaccine in the United States if approved.

Regulatory Status:

The FDA is reviewing Moderna's application with a decision expected by August 5. However, the approval process faced complications in February when the FDA initially rejected the application, arguing the company should have compared its vaccine against high-dose flu shots recommended for adults 65 and older in the U.S. The agency later reversed course and accepted an amended application, requiring Moderna to conduct additional studies in older adults post-approval. Regulatory reviews are also underway in the EU, Canada, and Australia.

Safety Profile:

Side effects—including injection-site pain, fatigue, headache, and muscle aches—were more common with the mRNA vaccine but generally mild to moderate and short-lived. Severe side effects occurred in 2.2% of mRNA recipients versus 1.9% with standard vaccines, indicating comparable safety profiles.

Market Implications:

The positive results arrive amid political scrutiny, as Health Secretary Robert F. Kennedy Jr., a known vaccine critic, has targeted mRNA technology for additional review. Approval would expand Moderna's mRNA platform beyond COVID-19 vaccines and potentially capture significant market share in the $6+ billion global flu vaccine market.