It is a combined vaccine against diphtheria, pertussis and tetanus. Pertussis is another name for whooping cough. The vaccine contains both diphtheria and tetanus toxoids, as well as killed pertussis (whooping cough) bacteria.
Toxoids are inactivated toxins. Toxins are produced by the diphtheria and tetanus bacteria and cause most of the clinical signs in these infections. Toxoids stimulate the body to produce immunity to these toxins.