The Food and Drug Administration (FDA) has approved Moderna's mResvia vaccine for the prevention of respiratory syncytial virus (RSV) in adults 60 years of age and older. This approval marks the entry of a third vaccine into the RSV market, following those from GSK (Arexvy) and Pfizer (Abrysvo). The CDC is expected to meet next month to provide recommendations on the shot’s use.
Addressing a Significant Public Health Need
RSV poses a significant threat to infants, the elderly, and immunocompromised individuals, potentially leading to severe disease and even death. The virus typically circulates during the fall and winter months, mirroring the seasonality of influenza and COVID-19. Amesh Adalja, an assistant professor at the Johns Hopkins Bloomberg School of Public Health, noted that RSV is now being recognized as an adult disease with considerable morbidity and mortality.
mResvia: An mRNA-Based Vaccine
mResvia leverages messenger RNA (mRNA) technology, similar to Moderna's COVID-19 vaccine. It is designed to train the body to recognize the prefusion F protein of RSV, a mechanism also employed by the vaccines from Pfizer and GSK. A key differentiator, according to Moderna CEO Stéphane Bancel, is mResvia's prefilled syringe formulation, which could ease the burden on pharmacies compared to the more complex administration requirements of its competitors.
Market Dynamics and Efficacy
Moderna anticipates a substantial RSV vaccine market, projecting annual sales between $6 billion and $8 billion. While some analysts suggest Moderna might face challenges as the third entrant, immunologist Dan Barouch from Harvard Medical School believes mResvia can perform well given the high demand for RSV vaccines. In clinical trials, mResvia demonstrated approximately 84% efficacy against RSV-related disease characterized by two or more symptoms. However, its effectiveness decreased to around 63% after 8.6 months, raising questions about the durability of protection compared to its rivals.
Safety Profile and Ongoing Monitoring
Clinical trials have indicated that all three approved RSV vaccines are generally safe, with common side effects including fatigue, headache, and injection site pain. The CDC is currently examining data suggesting a potential association between these vaccines and Guillain-Barré syndrome (GBS), a rare autoimmune disorder. While cases of GBS were reported in clinical testing for GSK's and Pfizer's vaccines, Moderna has not disclosed any cases from its trials. The CDC advisory committee has concluded that the benefits of Arexvy and Abrysvo outweigh the potential risks, while acknowledging the need for continued monitoring for a definitive link to GBS.
