Results from a prespecified pooled analysis of the pivotal Phase 3 MELODY and Phase 2b nirsevimab trials demonstrated an efficacy (relative risk reduction versus placebo) of 79.5% (95% CI 65.9 to 87.7; P<0.0001) against medically attended LRTI, such as bronchiolitis or pneumonia, caused by RSV in infants born at term or preterm entering their first RSV season.1

In a separate pooled post-hoc analysis of the trials, blood samples taken from infants dosed with nirsevimab exhibited RSV neutralizing antibodies that were approximately 50-fold higher than baseline at Day 151 post-dose. RSV neutralizing antibody levels remained greater than 19-fold higher than placebo recipients with no known RSV infection through Day 361, suggesting protection may extend beyond Day 151.2

The safety profile across the nirsevimab and placebo groups, as reported in previous trials, remains similar.3-6 These findings contribute to the growing body of evidence suggesting that nirsevimab can protect all infants through their first RSV season with a single dose.

Eric Simões, MD, Clinical Professor, Pediatrics-Infectious Diseases, UC Denver School of Medicine, “RSV remains the most common cause of LRTI in infants and results in seasonal epidemics globally each year. These new analyses strengthen nirsevimab’s potential to protect all infants across the RSV season with a single dose, which may lead to a paradigm shift in RSV prevention.”

Jean-François Toussaint, Global Head of Research and Development Vaccines, Sanofi, “These new analyses are very consistent with and confirm the strong results observed in all Phase 2 and Phase 3 studies that evaluated nirsevimab in diverse pediatric populations. We take pride in the progress made to develop a potential solution to address this long unmet need for all infants.”

Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca, “Each year, RSV causes seasonal epidemics of LRTIs in infants. These analyses add to nirsevimab’s compelling body of evidence as the first potential single-dose preventative immunization for all infants against RSV, addressing a clear unmet need in the RSV preventative landscape.”

The data are being presented at the 40th Annual Meeting of the European Society for Paediatric Infectious Diseases (ESPID) from May 9-13 in Athens, Greece.

Nirsevimab is being developed by Sanofi and AstraZeneca.