Introduction
lower respiratory tract infection, RSV infections, LRTI, infections
RSV INFECTION, RESPIRATORY SYNCYTIAL VIRUS (RSV), INFECTIONS, LOWER RESPIRATORY TRACT INFECTION, LRTI
Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection (LRTI) and hospitalization in infants and young children globallyNirsevimab is a recombinant human immunoglobulin G1 kappa monoclonal antibody with an extended half-lifeThe Phase 3 clinical trial of a previous investigational monoclonal antibody developed to prevent MA RSV LRTI in pre-term infants (suptavumab) failed to meet its primary endpoint because of the emergence of a newly circulating strain of RSV B with amino acid substitutions in the F protein that prevented binding to and neutralization of RSVThe aims of the present study were to genotypically evaluate RSV infections occurring in two pivotal nirsevimab clinical trials (Phase 2b: NCT02878330; MELODY: NCT03979313), characterize substitutions in the nirsevimab binding site, and determine their effects on nirsevimab susceptibility of RSV A and B isolates identified as causing infections. The prevalence of substitutions observed during these clinical trials was also evaluated in relation to changes observed across circulating RSV strains from surveillance data.