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.

Key Publications

• NEWJul Cost-benefit analysis of nirsevimab for respiratory syncytial virus prevention in infants: a population-based study. (European journal of pediatrics, 2026, PMID 42399582): "The present study aims to evaluate, from a public health perspective, the economic impact of implementing a universal immunization strategy with nirsevimab in the Community of Madrid (CM)."
• NEWJun Cost-effectiveness and public health impact of RSV immunization for all infants in Japan: a mixed strategy with nirsevimab and RSVpreF. (Expert review of vaccines, 2026, PMID 42334170): "With the approval of maternal immunization (MI) and nirsevimab, Japan is transitioning from high-risk-targeted prophylaxis toward broader RSV prevention."
• NEWJun Uptake and predictors of newborn respiratory syncytial virus (RSV) immunisation with nirsevimab in Ireland's national pilot programme: a cross-sectional study. (BMJ open, 2026, PMID 42331576): "To assess uptake of nirsevimab, a long-acting monoclonal antibody for respiratory syncytial virus (RSV) prevention, during the first season of Ireland's Pathfinder pilot universal newborn immunisation programme and to identify socio-demographic and perinatal predictors of uptake."
• NEWJun Acceptance of the respiratory syncytial virus infant monoclonal antibody nirsevimab among post-partum women in Italy. (Human vaccines & immunotherapeutics, 2026, PMID 42268596): "...the attitudes and the behaviors about the respiratory syncytial virus (RSV) infant monoclonal antibody and to explore any associations with different characteristics."
• NEWJun Economic evaluation of a bivalent respiratory syncytial virus prefusion F vaccine for maternal vaccination in Sweden: cost-effectiveness and budget impact. (Journal of medical economics, 2026, PMID 42258348): "To compare the clinical and economic outcomes of three infant RSV prevention strategies, monoclonal antibody prophylaxis with nirsevimab alone, maternal RSVpreF vaccination alone, and maternal RSVpreF vaccination with complementary nirsevimab versus no intervention in Sweden, to estimate cost-effectiveness and budget impact."
• Jun Real-world emergence of nirsevimab resistance in breakthrough infections with respiratory syncytial virus-B: a multicentre observational study in France. (The Lancet. Microbe, 2026, PMID 42229496): "Nirsevimab, a long-acting monoclonal antibody targeting a conserved epitope on the prefusion F protein (site Φ), has shown high efficacy in clinical trials and early real-world studies."
• May Infant respiratory syncytial virus (RSV) immunisation coverage in an Australian regional area, 1 May 2024 - 31 October 2025. (Communicable diseases intelligence (2018), 2026, PMID 42184438): "The recent introduction in Australia of respiratory syncytial virus (RSV) immunisations - nirsevimab (neonatal) and Abrysvo (antenatal) - offers potential to reduce the RSV burden in infants."
• Jun Modelling the impact of long-acting monoclonal antibody, maternal vaccine and hybrid programs of RSV immunisation in temperate Western Australia. (Vaccine, 2026, PMID 42176437): "Two RSV immunisations products: a maternal vaccine, Abrysvo, and a long-acting monoclonal antibody, nirsevimab, both designed to prevent RSV illness in infants, have recently become available."
• May Effectiveness of nirsevimab immunisation after birth versus RSVpreF maternal vaccination in preventing RSV-related hospitalisations in infants: a population-based retrospective cohort study. (The Lancet. Child & adolescent health, 2026, PMID 42107385): "Maternal respiratory syncytial virus (RSV) prefusion F (RSVpreF) vaccine and nirsevimab immunisation are two products recently implemented to reduce RSV-related lower respiratory tract infection (LRTI) in infants (nirsevimab since 2023 and RSVpreF since 2024)."
• Jun Maternal RSV Vaccination, Infant Nirsevimab, or Both: Interim Analysis of a Randomized Trial. (Pediatrics, 2026, PMID 42070784): "Although both maternal respiratory syncytial virus (RSV) prefusion F vaccination (RSVpreF) and infant nirsevimab immunization have been approved for the prevention of RSV lower respiratory tract infections, the 2 have not been evaluated in a single study, and their sequential administration has not been studied systematically."