Moderna's mRNA Flu Vaccine Outperforms Standard Shot in Phase III Trial

Moderna's mRNA-based seasonal influenza vaccine, mRNA-1010, has demonstrated superior efficacy compared to a currently licensed flu shot in a large-scale Phase III trial. The results, announced on June 30, 2025, mark a significant milestone for the company and pave the way for potential regulatory submissions and the development of combination vaccines.

Trial Results and Efficacy Data

The Phase III trial, which included over 40,000 participants across 11 countries, showed that mRNA-1010 was 26.6% more effective at preventing influenza in adults aged 50 years and older compared to a standard-dose seasonal flu vaccine. The efficacy was even higher in the 65 and older subgroup, with a 27.4% improvement over the licensed comparator.

Moderna's vaccine demonstrated enhanced protection against specific flu strains:

• 29.6% better efficacy against A/H1N1
• 22.2% better efficacy against A/H3N2
• 29.1% better efficacy against B/Victoria

These strains align with those included in the updated 2025-2026 influenza vaccine formulations, underlining the relevance of mRNA-1010's performance.

Safety Profile and Next Steps

The safety profile of mRNA-1010 appears favorable, with most adverse events reported as mild. Common side effects included injection site pain, fatigue, headaches, and myalgia. Moderna plans to present detailed findings at an upcoming scientific congress and engage with regulators regarding submissions for mRNA-1010.

Stéphane Bancel, Moderna's CEO, expressed confidence in the results, stating that they "pave the way for COVID-19 combination vaccines." This statement suggests that the company may revisit its plans for a combo flu/COVID-19 shot, following the withdrawal of its previous application in May 2025.

Broader Implications for mRNA Technology and Vaccine Development

The success of mRNA-1010 comes at a crucial time for the vaccine industry, which has faced recent challenges. Earlier in June, the CDC's vaccine advisory committee underwent significant changes, with new members known for their critical stance on vaccines. This restructuring has led to increased scrutiny of mRNA technology and vaccine safety.

Despite these headwinds, Moderna's positive trial results have bolstered investor confidence, with the company's stock rising approximately 5% in premarket trading following the announcement. The performance of mRNA-1010 not only represents a potential advancement in flu prevention but also reinforces the broader potential of mRNA technology in vaccine development.

As the pharmaceutical industry continues to navigate evolving regulatory landscapes and public health priorities, Moderna's latest achievement underscores the ongoing innovation in vaccine technology and its potential to address longstanding challenges in infectious disease prevention.