In addition to confirming the critical role of pertussis-specific Th17 cells, Antunes et al. also demonstrated the potential importance of (a) IL-9 secreting T-cells in vaccine-mediated protection and (b) regulatory cells that may inhibit T-memory-cell proliferation following pertussis booster vaccine in aP compared to wP-primed infants [109]. This evidence concerns the gene IL9 and pertussis.