National Respiratory Syncytial Virus (RSV) Awareness Month is observed each October in the US, to align with the start of RSV season. The campaign highlights the global health and economic burden of RSV, which poses serious risks to infants, older adults, and immunocompromised individuals, and encourages the public to engage in preventative measures, including immunization. Yet, despite recent breakthroughs in prophylaxis, treatment options for this common infection remain scarce, says GlobalData, a leading data and analytics company.

According to GlobalData forecasts, the US market alone will see sales of $2.7 billion in 2025, driven by the advances that have rapidly reshaped the RSV prophylaxis landscape. The country has seen the approval of multiple RSV prophylaxis products in the past two years, following decades of limited progress. These include the approval of novel monoclonal antibodies (mAbs) to protect infants; AstraZeneca/Sanofi’s Beyfortus (nirsevimab) in 2023 and Merck’s Enflonsia (clesrovimab) in 2025. In addition, several vaccines have been approved for the adult market. These include GSK’s Arexvy and Pfizer’s Abrysvo in 2023, as well as Moderna’s mRESVIA in 2024.

Abigail Harris, Infectious Disease Analyst at GlobalData, comments: “RSV innovation has accelerated at an unprecedented pace, with several prophylactic therapies now available. This has led to a decline in hospitalizations attributable to the infection. However, while prevention is improving, effective treatment options are virtually non-existent. Patients who develop severe RSV continue to rely on supportive care, with the broad-spectrum antiviral ribavirin offering limited efficacy and significant safety and access challenges.”

Developing antivirals for RSV has been challenging due to the virus’s genetic variability, lack of efficacy observed in clinical trials, and safety concerns in vulnerable populations such as infants and pregnant women.

Harris continues: “Without investment in the treatment of RSV, progress will remain incomplete. Prophylactic mAbs and vaccines can only go so far and there is a strong unmet need for novel therapeutics.”

There are, however, signs of progress. Companies active within this space include Enanta Pharmaceuticals, which has two direct acting antivirals in Phase II development. These are zelicapavir (EDP-938) and EDP-323, which target the N-protein and L-protein, respectively, both of which are essential for RSV replication.

Enanta Pharmaceuticals recently released topline results from RSVHR, its Phase IIb study of zelicapavir for the treatment of RSV in high-risk adults. The trial missed its primary endpoint of time to resolution of a subset of four lower respiratory tract disease symptoms to mild for zelicapavir relative to placebo. However, various other endpoints were met including time to improvement in the Patient Global Impression of Severity (PGI-S) score, and lower hospitalization rates, which resulted in a rise in stock value for the company.

Harris concludes: “Effective treatments are urgently needed to reduce RSV mortality and lessen the strain on health systems. Global health organizations, governments, and industry must prioritize not only expanding access to prophylactics but also accelerating R&D into therapeutics to close this critical gap.”