nirsevimab

Overview

Nirsevimab is a long-acting monoclonal antibody used for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in infants. It is designed as an immunoprophylactic therapy rather than a traditional vaccine: instead of stimulating the host to generate its own antibody response, it provides immediate passive protection through direct administration of an RSV-neutralizing antibody. Its clinical role is especially important in early infancy, when the risk of severe RSV disease is highest and when active immune responses may be less predictable.

Biologically, nirsevimab targets the RSV fusion (F) protein in its prefusion conformation, thereby blocking viral entry into host cells. Because it has been engineered for extended half-life, a single dose can provide protection across much of the RSV season. In recent public health practice, nirsevimab has been discussed alongside maternal RSVpreF vaccination as part of broader infant RSV prevention strategies.

Focus of Latest Publications

Recent publications on nirsevimab have focused on its real-world implementation, economic value, safety, uptake, and role within broader RSV prevention strategies for infants. Several studies evaluated population-level use in national or regional immunization programs, including universal newborn or infant prophylaxis campaigns in Madrid, Ireland, Australia, and Japan, as well as comparative strategy modeling alongside maternal RSVpreF vaccination. These reports reflect growing interest in how nirsevimab is being incorporated into routine public health programs and how it performs outside clinical trials.

Economic analyses were a prominent theme. In a population-based cost-benefit study from the Community of Madrid, universal infant immunization with nirsevimab was found to be cost-beneficial from both healthcare and societal perspectives, with lower healthcare event incidence among immunized children and positive returns across multiple dose-price scenarios. Another study in Japan examined the public health and economic impact of mixed RSV immunization strategies combining nirsevimab with maternal RSVpreF vaccination, while a Swedish economic evaluation compared nirsevimab alone, maternal vaccination alone, and a combined approach. Together, these publications emphasize the need to define the most efficient RSV prevention strategy for infants in different health systems.

Implementation and uptake studies also featured prominently. In Ireland’s national pilot universal newborn program, investigators assessed nirsevimab uptake and socio-demographic and perinatal predictors of receipt. In Australia, a regional cohort study described infant RSV immunization coverage during the transition from neonatal nirsevimab to antenatal Abrysvo, showing that overall coverage remained stable while the composition of protection shifted from nirsevimab to maternal vaccination. Survey-based studies in Italy and Greece examined parental and pediatrician attitudes, respectively, identifying generally favorable views toward RSV immunization but also highlighting the importance of trusted information sources, clinician counseling, and targeted education to support uptake and implementation.

Safety and resistance were additional areas of investigation. Post-licensure surveillance from Canada reported low rates of short-term health events after nirsevimab administration, including when co-administered with routine vaccines, with no anaphylaxis reported and overall good tolerability. In contrast, a multicentre observational study in France examined breakthrough RSV-B infections and the emergence of nirsevimab resistance, reflecting ongoing concern about escape variants despite the antibody’s established efficacy. Other studies compared nirsevimab with maternal RSVpreF vaccination in preventing RSV-related hospitalizations in infants, and an interim randomized trial evaluated maternal vaccination, infant nirsevimab, or both, underscoring the evolving evidence base for sequencing or combining these preventive approaches.