The lack of correlation between the percentage of CD11c+ and IgG1+ CD27+ Spike+ memory B cells following boosting or in the COVID-19-experienced PAD patients suggests that the defect in BCR signaling and IgG1 class-switching seen following primary vaccination might be overcome by additional costimulatory signals (Figures 4D; S5B). This evidence concerns the gene ITGAX and COVID-19.