Single-dose nirsevimab for prevention of RSV in preterm infants

Working as the Nirsevimab Study Group, researchers assessed whether the monoclonal antibody offers effective prophylaxis against respiratory syncytial virus (RSV) in infants.

Working as the Nirsevimab Study Group, researchers assessed whether the monoclonal antibody offers effective prophylaxis against respiratory syncytial virus (RSV) in infants. RSV is the primary cause of lower respiratory tract infection in this population, and the hope was that a single intramuscular dose would protect babies for an entire RSV season. Over a 1-year period, investigators randomized 969 premature but otherwise healthy infants to receive nirsevimab at the start of the RSV season. Another 484 babies were assigned to the control group, which received placebo. Medically attended RSV-associated lower respiratory tract infection occurred in 2.6% of the intervention group and 9.5% of the control group within 150 days after treatment administration, a difference of about 70%. Nirsevimab also reduced the rate of hospitalization for RSV-associated lower respiratory tract infection over that same time frame by more than 78%. The effects were observed across geographic locations (Northern vs. Southern Hemisphere) and RSV subtypes. A single injection of nirsevimab curtailed RSV-associated lower respiratory tract infections and related hospital admissions significantly more so than placebo, the researchers report, without producing additional safety concerns.