Moderna reports positive results from phase 3 efficacy study of P304 for seasonal influenza vaccine

Moderna reports positive results from phase 3 efficacy study of P304 for seasonal influenza vaccine

By, Admin 3 July 2025

Overview

Moderna, Inc, a leader in the creation of the field of mRNA medicine, announced positive results from a phase 3 efficacy study (P304) evaluating the relative vaccine efficacy (rVE) against influenza illness of mRNA-1010, the company's seasonal influenza (flu) vaccine candidate, compared to a licensed standard-dose seasonal influenza vaccine in adults aged 50 years and older. 
Results- mRNA-1010 achieved the most stringent superiority criterion prespecified in the protocol, with an rVE of 26.6% (95% CI; 16.7%, 35.4%) in the overall study population. Additionally, strong rVE was observed for each influenza strain contained in the vaccine, including A/H1N1 (rVE=29.6%), A/H3N2 (rVE=22.2%), and the B/Victoria lineages (rVE=29.1%). Subgroup analyses confirmed a consistently strong rVE point estimate across age groups, risk factors and previous influenza vaccination status. In participants aged 65 years and older, mRNA-1010 demonstrated an rVE of 27.4%.

Statement from CEO, Moderna on the positive outcomes 

Today's strong phase 3 efficacy results are a significant milestone in our effort to reduce the burden of influenza in older adults. The severity of this past flu season underscores the need for more effective vaccines,"" said Stéphane Bancel, CEO, Moderna. ""An mRNA-based flu vaccine has the potential advantage to more precisely match circulating strains, support rapid response in a future influenza pandemic, and pave the way for Covid-19 combination vaccines.""

mRNA-1010 Outperforms Flu Vaccines

In a previous phase 3 study, mRNA-1010 had already demonstrated superior seroconversion rates and geometric mean titer ratios (GMR) against all strains included in the vaccine compared to both high-dose and standard-dose licensed seasonal influenza vaccine.

Hosptalisation for seasonal flu

According to the CDC, seasonal flu-related hospitalizations and outpatient visits reached a 15-year high during the 2024-2025 season. More than 600,000 Americans were hospitalized due to flu-related illness last year, leading to substantial direct and indirect costs, as well as widespread disruption to daily life and work. 

The P304 trial

  • P304 is a phase 3, randomized, observer-blind, active-controlled, case-driven, pivotal efficacy, immunogenicity and safety study. 
  • The trial enrolled 40,805 adults aged 50 years and older across 11 countries. 
  • Participants were randomly assigned to receive either a single dose of mRNA-1010 or a standard-dose licensed comparator, with a median follow-up of six months.
  • Safety profile- Safety and tolerability of mRNA-1010 were consistent with reported results from a previous Phase 3 study.  The majority of solicited adverse reactions (SARs) were mild. Injection site pain was the most common local SAR, and fatigue, headache and myalgia were the most common systemic SARs reported. There were no significant differences between the groups in the rates of unsolicited adverse events, serious adverse events, or adverse events of special interest.

mRNA platform by Moderna

  • Moderna's mRNA platform has enabled the development of therapeutics and vaccines for infectious diseases, immuno-oncology, rare diseases and autoimmune diseases. 
  • With a unique culture and a global team driven by the Moderna values and mindsets to responsibly change the future of human health, Moderna strives to deliver the greatest possible impact to people through mRNA medicines.

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