Following vaccination with R21/Matrix M, NANP ₆ -reactive plasma antibody repertoires remain highly correlated before and after challenge with live sporozites. A subset of thrice-vaccinated VAC065 volunteers (n = 5) was analyzed at day 84 (pre-challenge; C₋₁) and 5 wk later at day 112 (post-challenge; C₊₃₅). (A and B) Relative abundance of NANP₆ reactive IgG lineages before and after challenge for one representative protected individual (A) and one non-protected individual (B). Each bar represents one lineage. Inset indicates relative abundance for each lineage before and after challenge (Pearson r² = 0.98 [A] and r² = 0.88 [B]). (C and D) Estimated plasma titer (C) and (D) change in titer of NANP₆-reactive IgG for volunteers before and after challenge (n = 17). Yellow markers indicate the group average. (E) Abundance of persistent antibodies before challenge (n = 5). (F) Abundance of emergent antibodies after challenge (n = 5). (G) Bray–Curtis dissimilarity index between pre- and post-challenge repertoires (n = 5). Lower values indicate higher degrees of similarity. Green indicates protection from infection; red indicates no protection. For each Ig-Seq analysis of polyclonal anti-NANP₆ IgG, the affinity purification was performed once, and the purified material was analyzed in triplicate by mass spectrometry.