GZMB and infection: Following natural infection, H3N2-LCII cases compared to No-LCII participants showed a significant increase in A/Victoria (H3N2)-stimulated GrB activity at 20-weeks post-vaccination; H3N2-LCII: 1447 (1198, 1745) vs No-LCII: 899 (854, 948) (Figure 2B, left panel; Supplemental Table S2; p < 0.001); but not B/Lee-stimulated GrB activity in H3N2-LCII: 767 (651, 904) vs No-LCII: 774 (734, 815) subsets (Figure 2B, right panel; Supplemental Table S2), consistent with an influenza A type-specific GrB response to natural infection.