Contraindications and Precautions Contraindications for DTaP and Tdap are A severe allergic reaction (eg, anaphylaxis) after a previous dose or to a vaccine component For the pertussis component: Encephalopathy (eg, coma, decreased level of consciousness, prolonged seizures) that occurred within 7 days of a previous dose of DTaP or Tdap and that is not attributable to another identifiable cause Because tetanus vaccination is important, people who have had an anaphylactic reaction to components in DTaP or Tdap should be referred to an allergist to determine whether they are allergic to tetanus toxoid.