what a tdap vaccine
DTaP[edit] DTaP (also DTPa and TDaP) is a combined vaccine against diphtheria, tetanus, and pertussis, in which the component with lower case 'a' is acellular. This is in contrast to whole-cell, inactivated DTP (aka DTwP). The acellular vaccine uses selected antigens of the pertussis pathogen to induce immunity.