Compared with WT infection or vaccination, BA.1, BA.2 and BA.5 breakthrough infections mainly elicit mAbs of groups E2.2, E3 and F1, which do not compete with ACE2 and demonstrate weak neutralizing activity, whereas WT-elicited antibodies enrich mAbs of groups A, B and C, which compete with ACE2 and exhibit strong neutralization potency (Fig. 3f–h). Here, ACE2 is linked to infection.