Nirsevimab is the first investigational immunisation designed to protect all infants across the RSV season with a single dose

Data analysis from pivotal phase 3 and phase 2b nirsevimab trials has demonstrated an efficacy of 79.5% against medically attended lower respiratory tract infections (LRTI), such as bronchiolitis or pneumonia. These conditions are often caused by a respiratory syncytial virus (RSV) among infants born at term or preterm, entering their first RSV season.

In the UK, RSV season occurs largely between November and April, with a peak in January to February. Outbreaks are most common in temperate climates during the winter months. RSV is a common respiratory virus, which can be serious for infants and older adults, causing pneumonia, respiratory distress and death among these populations.

Nirsevimab is the first investigational immunisation designed to protect all infants across the RSV season with a single dose.

“RSV remains the most common cause of LRTI in infants and results in seasonal epidemics globally each year,” explained Eric Simões, clinical professor, paediatrics-infectious diseases at UC Denver School of Medicine. “This new analysis strengthens 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.”

Nirsevimab is an investigational long-acting antibody designed to protect all infants from birth entering their first RSV season with a single dose.

In pooled post-hoc analysis of the trials, blood samples taken from infants dosed with nirsevimab exhibited RSV neutralising antibodies which were approximately 50-fold higher than baseline at day 151 post-dose.

Jean-François Toussaint, global head of R&D vaccines, Sanofi, said: “This new analysis is 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.”

“Each year, RSV causes seasonal epidemics of LRTIs in infants,” concluded Mene Pangalos, executive vice president, BioPharmaceuticals R&D at AstraZeneca. “This analysis adds to nirsevimab’s compelling body of evidence as the first potential single-dose preventative immunisation for all infants against RSV, addressing a clear unmet need in the RSV preventative landscape.”