Viral Genomic Sequencing

The study will test whether breakthrough infections are disproportionately associated with particular RSV viral groups. Respiratory samples will be screened by RT-qPCR for human RNase P, and only samples with cycle threshold values of 35 or lower will be included. Laboratory personnel interpreting tests will be blinded to participants' RSV monoclonal antibody or maternal vaccine exposure status. Sequencing reads will be aligned to RSV-A and RSV-B reference genomes, and lineages will be characterized using Nextstrain and maximum-likelihood phylogeny. The study includes genomic surveillance to detect RSV variants and assess whether lineages or mutations reduce protection.