Tetanus, diphtheria, pertussis/whooping cough vaccine (DTaP and Tdap) is an immunization used to protect against tetanus, diptheria, and pertussis (also known as whooping cough). Tetanus is a bacterial infection that can cause severe muscle spasms and can be fatal. Diphtheria is a bacterial infection that can cause breathing problems, heart failure, and paralysis. Pertussis, or whooping cough, is a highly contagious bacterial infection that causes severe coughing fits.