BCR and infection: To better understand predictors of cellular responses to SARS-CoV-2 mRNA vaccines in SCT recipients, we performed 10X single cell RNA-seq (scRNA-seq) combined with T Cell Receptor (TCR) and B Cell Receptor (BCR) sequencing on pre- and post-vaccination (2nd dose) samples, as well as post-infection samples when available, from 4 alloSCT recipients and 3 healthy controls.