Real-world HARMONIE clinical trial of nirsevimab reports 83% reduction in RSV infant hospitalizations

Sanofi announces new real-world evidence of nirsevimab’s efficacy and safety for protecting against infant RSV hospitalization in the HARMONIE real-world setting clinical trial 

New data from the real-world setting Hospitalized RSV Monoclonal Antibody Prevention (HARMONIE) Phase IIIb clinical trial of nirsevimab were presented at the 41st Annual Meeting of the European Society for Paediatric Infectious Diseases, and reported in a 12 May press release from Sanofi. The results show nirsevimab delivered an 83% reduction in infant hospitalizations due to respiratory syncytial virus (RSV) in a real-world clinical trial setting, reinforcing the evidence of nirsevimab’s protection against RSV-related lower respiratory tract disease (LRTD) and confirming its favorable safety profile in multi-country, real-world conditions.  

Nirsevimab, under development jointly by Sanofi and AstraZeneca, is a long-acting antibody designed to offer newborns and infants direct protection with a single dose against RSV disease from birth through their first RSV season, prior to the maturation of their immune systems. RSV is the most common cause of LRTD and a leading cause of hospitalization in infants globally. Following positive early results, nirsevimab was granted special designations to facilitate accelerated development by regulatory agencies around the world, including in China, Japan, the US, Europe and the UK.  

The HARMONIE study is a large, multi-country European interventional Phase IIIb clinical trial that aimed to determine the efficacy and safety of a single intramuscular dose of nirsevimab (<5 kg 50 mg; ≥5 kg 100 mg), compared to no intervention (standard of care), for the prevention of hospitalizations due to RSV-related LRTD in infants under 12 months of age who are not eligible to receive established palivizumab antibody therapy. The study was conducted in real-world settings during the 2022–2023 RSV season and recruited >8000 infants at nearly 250 sites across France, Germany and the UK. Sanofi and academic investigators worked together to design and deliver HARMONIE with digital solutions to minimize the burden on families, site staff and health systems.  

Three principal effects of the single-dose intervention were quantified in the new real-world data (RWD) from HARMONIE: 

• 83.21% (95% CI 67.77–92.04; P<0.001) reduction in infant hospitalizations due to RSV-related LRTD  
• 75.71% (95% CI 32.75–92.91; P<0.001) reduction in the incidence of hospitalizations due to severe RSV-related LRTD, defined as patients with oxygen levels <90% and requiring oxygen supplementation 
• 58.04% (95% CI 39.69–71.19; P<0.001) reduction in the incidence of all-cause LRTD hospitalization 

The HARMONIE RWD add to the body of evidence demonstrating nirsevimab’s protection against RSV-related LRTD and confirm its good safety profile in multi-country, real-world conditions.  

“This winter saw higher rates of RSV-related infant hospitalizations than during pandemic or pre-pandemic years. The HARMONIE data demonstrate the real-world impact nirsevimab has on pediatric hospitalizations, and illustrate its importance for infants, their families and public health,” asserted Sanofi Executive Vice President of Vaccines, Thomas Triomphe.  

Simon Drysdale, Co-Chief Investigator of HARMONIE and Consultant Pediatrician in Infectious Diseases at St George’s University Hospital NHS Foundation Trust said:
“RSV-related chest infections lead to high numbers of infants under 12-months old being hospitalized every year. These data reinforce the potential public health benefit of nirsevimab in terms of helping to reduce the strain on hospitals caused each year by RSV.”