Study population
respiratory illness
LRTI
Together, the Phase 2b and MELODY trials enrolled infants across 4 years in both the Northern and Southern Hemispheres in both inpatient and outpatient settings. The Phase 2b study was performed at 164 sites in 23 countries; MELODY was performed at 160 sites in 21 countries. Of 1453 participants randomized in Phase 2b trial, next-generation sequencing (NGS)-evaluable RSV isolates were identified in 40 of 969 nirsevimab recipients and 54 of 484 placebo recipients who had suspected LRTI or any respiratory illness requiring hospitalization over 360 days post-dose. Of those who received nirsevimab, 17 received 50 mg nirsevimab and were <5 kg in body weight at the time of injection, in line with the subsequent weight-banded dosing regimen, whereas 23 participants received 50 mg nirsevimab but were ≥5 kg and thus received a dose that was later determined to result in suboptimal exposures to nirsevimab (Supplementary Fig. 