Moderna Reports Adult RSV Vaccine Efficacy of 84% in Phase 3 ConquerRSV Trial

Biotechnology company Moderna announced Tuesday that its investigational vaccine against respiratory syncytial virus (RSV) in adults met its primary efficacy endpoints, including vaccine efficacy (VE) of 83.7% against RSV-associated lower respiratory tract disease (RSV-LRTD) defined by ≥2 symptoms and 82.4% against disease defined by ≥3 symptoms.

The results, from the phase 3 ConquerRSV trial of mRNA-1345, followed review by an independent Data Safety Monitoring Board (DSMB) and provide the foundation for the company's planned regulatory submission in the first half of 2023.

"Today's results represent an important step forward in preventing lower respiratory disease due to RSV in adults 60 years of age and older. These data are encouraging and represent the second demonstration of positive phase 3 trial results from our mRNA infectious disease vaccine platform, after Spikevax, our COVID-19 vaccine. We look forward to publishing the full data set and sharing the results at an upcoming infectious disease medical conference," said Stéphane Bancel, Moderna's chief executive officer.

The randomized, double-blind placebo controlled ConquerRSV trial enrolled approximately 37 000 adults aged ≥60 years across 22 countries (NCT05127434). Two definitions of RSV-LRTD served as primary efficacy endpoints: ≥2 or ≥3 symptoms of disease.

Findings from the interim analysis were based on 64 cases of RSV-LRTD with ≥2 symptoms, with 55 observed in the placebo group and 9 in the mRNA-1345 group, as well as 20 cases of RSV-LRTD with ≥3 symptoms, of which 17 cases occurred in placebo-treated participants vs 3 in the mRNA-1345 active treatment group. The VE against RSV-LRTD defined by ≥2 symptoms was 83.7% (95.88% CI: 66.1%, 92.2%; P<.001) and against RSV-LRTD defined by ≥3 symptoms was 82.4% (96.36% CI: 34.8%, 95.3%; P=.0078).

According to Moderna, there are additional efficacy analyses planned as cases accrue during the ongoing trial and will include VE against severe RSV.

The DSMB found no safety concerns after reviewing available data and reports further that mRNA-1345 appears well tolerated. The majority of solicited adverse reactions ranged from mild to moderate and most commonly included injection site reaction, fatigue, headache, myalgia, and arthralgia, according to the Moderna announcement. Safety and tolerability will be monitored throughout the balance of the study and updated analyses will accompany the regulatory submission, the company said.

"RSV significantly affects the health of older and high-risk adults, particularly those with comorbidities," said Abdullah Baqui, a principal investigator for the study sites in Bangladesh and professor, Department of International Health, director, International Center for Maternal and Newborn Health, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University. The results of ConqueRSV will increase understanding of the “role of severe acute respiratory infections in older adult populations and inform the future implementation of vaccines in adults in lower-resource areas," he added.

The company plans to submit the study data for publication in a peer-reviewed publication and to present findings at an upcoming scientific meeting.