Single-dose nirsevimab prevents RSV-associated LRTI in preterm infants

A single-dose of nirsevimab helps prevent respiratory syncytial virus (RSV)-associated lower respiratory tract infection (LRTI) in preterm infants during an entire RSV season, according to a recent study.

This study involved 1,453 healthy preterm infants who were recruited from 164 sites in 23 countries between November 3, 2016 and December 1, 2017. Participants were randomized in a 2:1 ratio to receive either a single intramuscular injection of nirsevimab 50 mg (n=969, mean age 3.29 months) or placebo (n=484, mean age 3.28 months) within 2 months prior to the RSV season and were monitored for medically attended respiratory illnesses for 150 days. [N Engl J Med 2020;383:415-425]

A significantly lower incidence of medically attended RSV-associated LRTI was observed in the nirsevimab arm than the placebo arm (2.6 percent vs 9.5 percent; relative difference, 70.1 percent, 95 percent confidence interval [CI], 52.3–81.2; p<0.001).

There was also a lower incidence of hospitalization due to RSV-associated LRTI among those treated with nirsevimab compared with placebo (0.8 percent vs 4.1 percent; relative difference, 78.4 percent, 95 percent CI, 51.9–90.3; p<0.001).

“[Overall, the] differences were consistent throughout the 150-day period after the dose was administered and across geographic locations and RSV subtypes,” the researchers noted.

Adverse events were comparable between the nirsevimab and placebo arms (86.2 percent vs 86.8 percent), with no incidents of anaphylaxis or other notable hypersensitivity reactions, said the researchers.

“[Previous studies have shown that] RSV is the most common cause of lower respiratory tract disease and hospitalizations for respiratory illness among infants and young children, resulting in largely predictable annual epidemics worldwide,” according to the researchers. [Lancet 2017;390: 946-958; N Engl J Med 2015;372:835-845]

“This trial of … [nirsevimab] showed that a single intramuscular dose of RSV immunoprophylaxis could protect infants against RSV-associated LRTI requiring medical attention [and hospitalizations for 150 days], … the length of a typical RSV season,” they concluded.