Moderna’s messenger RNA vaccine for respiratory syncytial virus (RSV) has received FDA approval, an authorization that arrives nearly a year after GSK and Pfizer secured their own regulatory approvals for RSV vaccines. The FDA’s recent decision pertains to adults aged 60 and older. Marketed as mResvia, the vaccine is expected to be available before the onset of the 2024/2025 respiratory virus season.
The next step for mResvia is obtaining a recommendation from the Centers for Disease Control and Prevention’s Advisory Committee on Vaccination Practices (ACIP). The vaccine is on the agenda for the committee’s upcoming meeting in late June.
RSV is known to cause symptoms similar to the common cold, but it can lead to serious respiratory infections, particularly in young children and the elderly with weaker immune systems. While GSK’s Arexvy and Pfizer’s Abrysvo induce an immune response against the prefusion F protein on the surface of RSV, Moderna’s mResvia employs a different technological approach. It uses a messenger RNA sequence to encode a stabilized version of this protein, sparking an immune response. This technology is derived from the same platform used for Moderna’s mRNA Covid-19 vaccine, Spikevax.
FDA approval of mResvia is grounded in Phase 3 study results involving around 37,000 older adults across 22 countries. Initial results demonstrated 83.7% efficacy against RSV lower respiratory tract disease. Follow-up analyses revealed a slight dip in efficacy to 78.7%, with a longer-term efficacy standing at 62.5%
Cross-trial comparisons indicate that mResvia’s efficacy is slightly below that of GSK’s Arexvy, which reported 82.6% efficacy with a median follow-up of 6.7 months. Pfizer’s Abrysvo showed 66.7% efficacy with a median follow-up of 7 months. Analysts noted that these differences could be attributed to varying trial methodologies and follow-up periods.
In terms of safety, Moderna’s mResvia appears to have an edge. The study reported no serious safety concerns, with common adverse reactions being injection site pain, fatigue, headache, and muscle and joint pain. Contrarily, GSK’s Arexvy trial reported cases of brain and spinal cord inflammation, and one case of Guillain-Barre syndrome, prompting the FDA to mandate further risk assessments. Similar concerns were noted in Pfizer’s trials, but no additional testing was required.
Despite the safety advantages, GSK’s Arexvy remains the market leader, with sales reaching approximately $1.5 billion in 2023, followed by Pfizer’s Abrysvo at about $850 million. Moderna’s success with mResvia is critical to counterbalance declining revenues from Spikevax amidst waning demand for Covid-19 vaccines.
Moderna plans to differentiate mResvia through ease of administration, offering it in prefilled syringes to save time and reduce errors, unlike the vial forms of Arexvy and Abrysvo. Analysts have shown mixed reactions to this strategy. Some view the convenience factor favorably, while others remain skeptical, emphasizing that clinical efficacy will likely play a more crucial role in market competition.
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