More sustained protection is associated with skewed CD4+ T-cell programming: natural infection and priming with whole cell pertussis vaccination induce programming towards T helper (Th1) and Th17 CD4+ T cells, as opposed to Th2/Th17 skewed CD4+ T-cell memory responses induced by acellular pertussis vaccination (Ryan et al., 1998; Esposito et al., 2001; Mascart et al., 2003; Vermeulen et al., 2010; Warfel et al., 2014). Here, CD4 is linked to infection.