We found a strong correlation between IgG PB response and PD-1 upregulation within CXCR3+CCR6-CCR7- cTFH and CXCR3+CCR6-CCR7+ cTFH in HC who received Fluvax (Fig 9A and 9B), but not in CKD after Fluvax, or after HBV in any group. Here, CCR6 is linked to chronic kidney disease.