Moderna’s RSV Vaccine Demonstrates Safety and Efficacy for 8 Months


The investigational vaccine, mRNA-1345, developed for seniors has its FDA PDUFA date in a few days.

a provider loading up a RSV vaccine. Image credit: Unsplash

Last year, Moderna shared results of its phase 3 trial, ConquerRSV, demonstrating their RSV vaccine had an efficacy of 83.7% against RSV-LRTD.

Image credit: Unsplash

This Sunday, May 12, marks the FDA PDUFA date for Moderna’s RSV vaccine, mRNA-1345. Ahead of the potential approval, follow-up data on the vaccine is being presented at this week’s NFID 2024 The Annual Conference on Vaccinology Research (ACVR).

The company’s RSV vaccine was developed to prevent against RSV-associated lower respiratory tract disease (RSV-LRTD) in seniors 60 years of age and older.

According to a NFID 2024 ACVR oral abstract, additional analyses was performed when >90% of participants completed a ≥6-month follow-up, post administration. “A single dose of mRNA-1345 was well-tolerated, with no safety concerns identified, and continued to demonstrate efficacy for the prevention of RSV disease through ≥8 months among adults ≥60 years,” the investigators wrote. "At a median follow-up of 8.6 months, mRNA-1345 vaccine efficacy was 63.3%, 63.0%, and 53.9% against RSV-LRTD with ≥2 and ≥3 symptoms and RSV-associated acute respiratory disease, respectively."1

What You Need to Know

Efficacy and Safety: Moderna's RSV vaccine, mRNA-1345, has shown promising efficacy and safety profiles in clinical trials. With efficacy rates around 83.7% against RSV-associated lower respiratory tract disease (RSV-LRTD) in seniors, and with no safety concerns identified, the vaccine demonstrates potential in preventing RSV-related illnesses among older adults.

Long-term Protection: Follow-up data presented at the NFID 2024 ACVR indicates that a single dose of mRNA-1345 continues to demonstrate efficacy for the prevention of RSV disease through at least 8 months among adults aged 60 and older.

Vaccine Composition: mRNA-1345 is composed of a single mRNA sequence encoding a stabilized prefusion F glycoprotein, utilizing lipid nanoparticles (LNPs) similar to Moderna's COVID-19 vaccines.

Previous Data
The ConquerRSV trial is a randomized, double-blind, placebo-controlled study of approximately 37,000 adults 60 years or older in 22 countries, including the United States. The primary efficacy endpoints were based on 2 definitions of RSV-LRTD defined as either 2 or more symptoms, or 3 or more symptoms of disease.2

The interim analysis was based on 64 cases of RSV-LRTD with two or more symptoms, of which 55 occurred in the placebo group and 9 occurred in the mRNA-1345 group, and 20 cases of RSV-LRTD with three or more symptoms, of which 17 cases were observed in the placebo group compared with three cases observed in the mRNA-1345 group.2

The other primary efficacy endpoint against RSV-LRTD defined by three or more symptoms was also met, with a VE of 82.4% (96.36% CI: 34.8%, 95.3%; p=0.0078).2

The company reported that the mRNA-1345 vaccine was well tolerated with no safety concerns identified. To date most solicited adverse reactions were mild or moderate and the most commonly reported solicited adverse reactions in the mRNA-1345 group were injection site pain, fatigue, headache, myalgia, and arthralgia.2

The overall rate of severe (Grade 3 or greater) solicited systemic adverse reactions was 4.0% for mRNA-1345 and 2.8% for placebo. The overall rate of Grade 3 or greater solicited local adverse reactions was 3.2% for mRNA-1345 and 1.7% for placebo. The study is ongoing, and an updated analysis of safety and tolerability will be provided at the time of regulatory submission.2

Vaccine Composition and the Upcoming PDUFA
The vaccine is made up of a single mRNA sequence encoding for a stabilized prefusion F glycoprotein. The vaccine uses the same lipid nanoparticles (LNPs) as in the Moderna COVID-19 vaccines. The F glycoprotein is on the surface of the virus and is required for infection by helping the virus to enter host cells. It exists in two states, prefusion and postfusion. The prefusion conformation is a significant target of potent neutralizing antibodies and is highly conserved across both RSV-A and RSV-B subtypes.2

In the coming days, an FDA decision will be made about Moderna’s RSV vaccine for seniors, so be sure to check back on Contagion later this week to read the news on the mRNA-1345 decision.

1.Wilson E, Goswami J, et al. Efficacy and Safety of mRNA-1345, an RSV Vaccine, in Older Adults: Results through ≥ 6 Months of Follow-up Oral Abstract #07 presented at NFID 2024 ACVR. May 8-10, 2024. online.

2.Parkinson J. Moderna RSV Vaccine for Seniors Meets Primary Endpoints for its Phase 3 Trial. Contagion. January 17, 2023. Accessed May 8, 2024.

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