Source:
Investigators from multiple institutions conducted a randomized controlled trial to assess the efficacy and safety of nirsevimab in preventing respiratory syncytial virus (RSV)-associated lower respiratory tract infections in healthy late-preterm and term infants. Participants were healthy infants <1 year old who had been born at ≥35 weeks’ gestation and were entering their first RSV season; infants were enrolled at 160 sites in 21 countries. Study children were randomized in a 2:1 ratio to receive a single intramuscular dose of nirsevimab (50 mg for those weighing <5.0 kg or 150 mg for children weighing ≥5 kg) or placebo. Randomization was stratified by age category (≤3 months, 3-6 months, >6 months). The primary study outcome was medically attended RSV-associated lower respiratory tract infection, defined as signs and symptoms of lower respiratory tract disease in a child with RSV detected by PCR, through 150 days after injection of study drug. Secondary outcomes included hospitalization for RSV-associated lower respiratory tract disease. Poisson regression was used to calculate the relative risk of these outcomes in infants randomized to nirsevimab compared to placebo recipients, after adjusting for age group at randomization. The efficacy of nirsevimab was calculated as 1 minus relative risk. Adverse events, occurring up to 360 days after injection in study participants, also were documented.
Among 1,490 children randomized, 1,478 received an injection of study drug, including 987 infants randomized to nirsevimab and 491 placebo recipients; 1,465 completed 150 days of follow-up. The median age of participants at enrollment was 2.60 months (range, 0.03, 11.10), and 86% were born at ≥37 weeks’ gestation. Medically attended RSV-associated lower respiratory tract infection occurred in 12 (1.2%) infants receiving nirsevimab and 25 (5.0%) placebo recipients, yielding a calculated efficacy of nirsevimab of 74.5% (95% confidence interval [CI], 49.6, 87.1; P <0.001). There were 6 (0.6%) and 8 (1.6%) infants, respectively, receiving nirservimab or placebo who were hospitalized for RSV-associated lower respiratory tract disease (efficacy, 62.1%; 95% CI, -8.6, 86.8; P = 0.07). Overall, ≥1 adverse event was reported in 87.4% of infants receiving nirsevimab and 86.8% of those randomized to placebo. An adverse event thought to be related to study participation occurred in 1.0% and 1.4%, respectively, of those randomized to nirsevimab or placebo. Three children in the nirsevimab group died in the 360 days after injection; none of the deaths were thought to be related to participation in the study.
The authors conclude that a single dose of nirsevimab was effective in preventing medically attended RSV-associated lower respiratory tract infection in healthy late-preterm and term infants.
Dr Lesser has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
RSV can cause severe lower respiratory tract infection and is a leading cause...
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