The European Commission approved Merck's ENFLONSIA (clesrovimab) on April 17, 2026, for preventing RSV lower respiratory tract disease in neonates and infants during their first RSV season.123
ENFLONSIA is the first RSV preventive in the EU with fixed, non-weight-based dosing (105 mg/0.7 mL), providing protection for up to 5 months.15
Approval covers all 27 EU member states plus Iceland, Liechtenstein, and Norway; availability varies by country due to reimbursement processes.1
Supported by Phase 2b/3 CLEVER and Phase 3 SMART trials, showing significant reductions in RSV disease and hospitalizations; data published in NEJM in September 2025.1
Common side effects include injection-site pain (6.5%), erythema (4.4%), swelling (3.2%), and rash (2.3%), mostly mild or moderate.12
ENFLONSIA is already approved in the US, Canada, Switzerland, and other countries.1
Sources:
1. https://www.merck.com/news/european-commission-approves-mercks-enflonsia-clesrovimab-for-the-prevention-of-respiratory-syncytial-virus-rsv-lower-respiratory-tract-disease-in-infants-during-their-first-rsv/
2. https://www.ema.europa.eu/en/medicines/human/EPAR/enflonsia