RSV image from National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIH)
This year’s IDWeek (Oct 19-22, 2025) showcased a spectrum of therapeutics to protect against and treat Respiratory syncytial virus (RSV) infection across vulnerable populations: infants, older adults, and the immunocompromised. Once dominated by seasonal hospital surges and limited preventive options, RSV management is entering a new era characterized by durable vaccination strategies, next-generation monoclonal antibodies, and the emergence of targeted antiviral therapy.
Prevention for adults: Durable and effective options for adults
In the adult market, Pfizer strengthened its leadership in the RSV space by reframing RSV vaccination from a single-season intervention toward a durable, high-impact protection strategy for older adults and at-risk populations. Two years after its initial approval, Abrysvo is building a strong RWE foundation that is increasingly difficult for future entrants to match. New Kaiser Permanente Southern California data demonstrated 75% effectiveness against RSV-associated hospitalization and emergency department visits sustained across two seasons, with no observable waning through approximately 12 months post-vaccination. The vaccine’s consistent performance across RSV-A and RSV-B, and in older, comorbid adults, strengthens Pfizer’s scientific and commercial narrative and positions durability as the next competitive frontier.
Pfizer’s DAN-RSV trial further reinforced Abrysvo’s clinical footprint in high-risk populations, demonstrating 60.5% vaccine effectiveness in immunosuppressed individuals and 92.3% in non-immunosuppressed adults. Crucially, vaccine-associated absolute hospitalization reductions were more than five-fold higher in immunosuppressed adults. These results align with the ACIP’s April decision to expand adult RSV vaccination eligibility to those aged ≥50 years at increased risk, unlocking a larger eligible population and providing Pfizer with a policy tailwind ahead of competitive launches. Despite launching after GSK’s Arexvy, the growing evidence base gives Pfizer a strengthening clinical and real-world story that supports its position in the adult RSV market redefine the adult RSV space.
Moderna, meanwhile, is positioning itself to compete not through breadth but through strategic specialization. The company is targeting the severely immunocompromised population, with its mRNA vaccine, mRESVIA. Phase 3 data in solid organ transplant recipients demonstrated strong, durable responses across transplant types, including in severely immunocompromised adults. Moderna’s focused strategy could allow the company to establish category leadership in a niche with high unmet need.
Prevention for infants: A new competitive landscape
In the infant prevention market, the June 2025 approval of Merck’s Enflonsia (clesrovimab) marks the first entry of a competitor to Sanofi’s Beyfortus, introducing choice for pediatricians and public health systems for the first time. While Beyfortus, which requires weight-based dosing, holds the first to market advantage, Merck is differentiating itself through its single fixed-dose, prefilled format. Enflonsia’s clinical performance, showing an 84% reduction in RSV-related hospitalizations and a 60% decline in medically attended lower respiratory tract infections (MALRI) through five months, positions it as a potent, single-dose alternative to Beyfortus. Exploratory CLEVER trial analyses presented at ID Week 2025 showed comparable non-RSV respiratory infection and coinfection rates between Enflonsia and placebo groups, reinforcing its clean clinical profile.
However, the infant space is not purely a monoclonal antibody battle. Maternal vaccination adds a parallel pathway for infant RSV protection. Phase 4 data in 181 mother-infant pairs validated maternal Abrysvo, infant Beyfortus, and the combination regimen make a safe and synergistic approach, showing strong antibody transfer and sustained infant protection through four months. This evidence reinforces the value of a flexible “either or both” prevention model. Having two validated pathways for infants increases overall protection, allowing both Beyfortus and Abrysvo to coexist in the market while targeting complementary patient populations and care settings.
Unlocking the next RSV market opportunities: Therapeutics and combination strategies
The development of RSV therapeutics represents the next major opportunity in the market. Enanta’s EDP-323, an oral L-protein polymerase inhibitor, meaningfully advances treatment prospects. Human challenge data showed rapid reductions in symptom burden and viral load within 24 hours, with symptom AUC reductions of 73% and 61% and viral load AUC declines of 85-87%, alongside strong tolerability. If later-stage trials replicate these findings, RSV could shift from a prevention-only market to a prevention and treatment commercial model, enabling retail pharmacy prescribing, outpatient treatment, and new payer economics. This opens opportunities for post-exposure prophylaxis and outbreak control in high-risk settings such as long-term care, oncology units, NICUs, and transplant centers.
The next stage of RSV competition will be driven by strategic portfolio management and expansion into complementary segments, rather than single-product performance. Combination respiratory vaccines (e.g., RSV + hMPV) could redefine seasonal immunization by consolidating protection, improving compliance, and upgrading value. Expanding RSV vaccination to toddlers and young children could drive significant volume growth, though it depends on demonstrating safety and building trust in pediatric populations. Post-exposure prophylaxis is an untapped opportunity where fast-acting antivirals or monoclonal antibodies could provide strong clinical value and justify premium pricing. Ultimately, success in RSV will depend on companies that combine real-world evidence with strategic segment focus, smart lifecycle planning, and the ability to expand from one population to multiple patient groups.
About the authors
Maryam Youssef
Maryam Youssef serves as a Junior Business Analyst at Lifescience Dynamics, supporting projects across various therapeutic areas such as vaccines, rare diseases, and oncology. She holds a Master’s degree from McGill University, where she specialized in mRNA therapeutics and viral vector biomanufacturing. Maryam brings a strong scientific foundation to her consulting work, enabling her to contribute meaningful analysis and support to clients in the life sciences sector.
Pooja Goyal
Pooja Goyal is a Senior Consultant based out of Lifescience Dynamics’ Toronto office. She has over 9 years of experience in the pharmaceutical consulting industry. Pooja brings expertise in competitive intelligence, opportunity assessment, market access and pricing and disease area strategy projects in immunology and other therapy areas. During early part of career, she has also worked in the analytical R&D of a leading ophthalmic manufacturing firm. Pooja holds an M.S.(Pharm.) in Medicinal Chemistry from National Institute of Pharmaceutical Education and Research (NIPER), Mohali, India and a Bachelor in Pharmaceutical Science from Panjab University, Chandigarh, India.
Yushi Redhead
Yushi Redhead is a Consultant at Lifescience Dynamics with a diverse research background in both academic and industry settings. He has extensive experience in conducting CI and primary research across a wide range of indications including, infectious diseases (COVID, RSV, Influenza), oncology and women’s health. Yushi has a PhD in Developmental Biology from King’s College London / The Francis Crick Institute, MSc in Clinical Neuroscience from University College London and BSc in Biochemistry from Swansea University.
Filed Under: Infectious Disease
