respiratory syncytial virus

RSV Long-Acting Antibody Effective in Protecting Infants, Reducing Hospitalization in Infants

Jessica Ganga

According to a recent study, one dose of nirsevimab effectively protected preterm infants and infants born at term from respiratory syncytial virus (RSV) and RSV lower respiratory tract infection (LRTI).1

In the United States, RSV leads to approximately 58,000 to 80,000 hospitalizations per year among children aged 5 years and younger, according to the CDC.2 Further, the disease causes about 100 to 300 deaths in that same population per year.2

Enter Simões and colleagues, whose study follows three trials that examined the efficacy of nirsevimab—a monoclonal antibody that protects infants from RSV and RSV LRTI, as well as infants considered high risk for severe RSV. Efficacy was determined by two endpoints that included the incidence of medical care for RSV LRTI and the number of hospital admissions for RSV LRTI.

In total, 2350 infants were enrolled in the phase 2b and MELODY trials, where they were randomized into two groups. One group (n = 1564) received a single nirsevimab injection prior to the RSV season. And the other group (n = 786) received placebo. Additionally, infants in the MEDLEY trials that tested nirsevimab on infants with chronic lung disease, congenital heart disease, or extreme preterm birth received one dose of nirsevimab followed by four monthly placebo doses, or five once-a-month doses of palivizumab.

Nirsevimab showed efficacy in reducing the number of infants medically cared for, hospital admissions, and relative risk reduction when compared to the placebo group. Infants at a high risk were effectively protected by nirsevimab as well, according to the study’s data. For patients with only LRTI, there were fewer any-cause medical care, any-cause hospital admissions, LRTI outpatient visits, and antibiotic prescriptions.

Additionally, the MEDLEY trials examined the effectiveness of nirsevimab in infants with chronic lung disease, congenital heart disease, or extreme preterm birth. Their data found that the use of nirsevimab in that patient population was consistent with the above findings, with more exposures of nirsevimab reaching above target in more than 80% of the overall MEDLEY trial population.

The authors noted that their study was funded by AstraZeneca and Sanofi, which developed and commercialized nirsevimab.

“These data suggest that nirsevimab has the potential to change the landscape of infant RSV disease by reducing a major cause of infant morbidity and the consequent burden on caregivers, clinicians, and health care providers,” the researchers concluded.



  1. Simões EAF, Madhi SA, Muller WJ, et al. Efficacy of nirsevimab against respiratory syncytial virus lower respiratory tract infections in preterm and term infants, and pharmacokinetic extrapolation to infants with congenital heart disease and chronic lung disease: a pooled analysis of randomised controlled trials. Lancet Child Adolesc Health. Published online January 9, 2023. doi:10.1016./S2352-4642(22)00321-2
  2. RSV Research & Surveillance. Centers for Disease Control and Prevention. October 28, 2022. Accessed January 24, 2023.