In 1995, a 46-year-old man presented with toxigenic diphtheria of the nasal cavity, pharynx, larynx and trachea. It was not known whether he had ever been immunized but, certainly, no booster immunization had been given during the previous 30 years. The patient was ill for 5 days before admission to hospital. The first symptom was a sore throat, but no medical advice was sought. After 2 days, his sore throat worsened, his temperature increased and he noticed swelling of the tonsillar region and a nasal discharge; 4 days later, he had marked swelling of the neck. On the night before admission, he was unable to sleep. On admission, he had a serosanguineous nasal discharge and inflammation of the palate, pharynx and tonsils, with a whitish membrane extending to the uvula. The larynx and vocal cords could not be visualized. There was hyperemia of the face and neck with soft tissue edema down to the level of the clavicles as well as tachypnea, tachycardia and arterial hypertension with respiratory distress, indicating respiratory obstruction and respiratory insufficiency. A diagnosis of diphtheria was made. Throat and nasopharyngeal swabs including particles of membrane were taken for culture. These later yielded toxigenic Corynebucterium diphtheriae var gruois. Because the clinical picture strongly suggested diphtheria, specific treatment with antitoxin and antibiotics was initiated immediately. The skin test for