In a recent Tdap booster trial, the IgG antibody concentrations, pertussis toxin (PT) neutralizing antibody (PTNA) capability, and frequencies of memory B cells were reported after acellular pertussis (aP) booster vaccination in four age groups with different vaccine priming backgrounds, in Finland, the Netherlands, and the United Kingdom (UK) [7,27,28]. This evidence concerns the gene F2 and pertussis.