ABSTRACT
The rapid evolution of SARS-CoV-2 is driven in part by a need to evade the antibody response in the face of herd immunity. Here, we isolate spike binding monoclonal antibodies (mAbs) from vaccinees who suffered vaccine break-through infections with Omicron sub lineages BA.4 or BA.5. 28 potent antibodies were isolated and characterised functionally, and in some cases structurally. Since the emergence of BA.4/5 SARS-CoV-2 has continued to accrue mutations in the S protein, to understand this we characterize neutralization of a large panel of variants and demonstrate a steady attrition of neutralization by the panel of BA.4/5 mAbs culminating in total loss of function with recent XBB.1.5.70 variants containing the so-called ‘FLip’mutations at positions 455 and 456. Interestingly, activity of some mAbs is regained on the recently reported variant BA.2.86.