The extended half-life monoclonal antibody nirsevimab protected term and late-preterm infants against hospitalization for respiratory syncytial virus (RSV)-associated lower respiratory tract infection and very severe medically attended RSV-associated lower respiratory tract infection during an RSV season, the authors of a letter report. In the phase 3 MELODY trial, 3,012 infants randomly received nirsevimab 50 mg (weight <5 kg) or 100 mg (weight of 5 kg or more) or placebo.
The results were as follows: “A total of 37 of 1,701 nirsevimab recipients and 35 of 849 placebo recipients were hospitalized for lower respiratory tract infection of any cause. With the exclusion of participants who were enrolled in South Africa, where there was no RSV transmission during the Covid-19 pandemic, the number needed to treat to prevent one hospitalization for lower respiratory tract infection of any cause was 53.1 (95% CI, 29.4 to 250.0), a number that was consistent with that in the primary cohort in the MELODY trial. Furthermore, an estimated 57 days of hospitalization for lower respiratory tract infection of any cause were averted for every 1,000 infants who received nirsevimab.
“Adverse events related to nirsevimab or placebo were reported in 1.3% of the nirsevimab recipients and 1.5% of the placebo recipients through 360 days after injection.”