Postimmunization (vaccination) injection-site reactions. A report of four cases and review of the literature.

Four patients each had a single subcutaneous nodule at the site of a previous vaccine injection; three after injection of diphtheria, tetanus, and pertussis vaccination and one after tetanus toxoid vaccination. Presentation was with a mass 4-22 months after vaccination at the site of injection. Histologically, three patients had a necrotizing granulomatous reaction with a surrounding infiltrate of lymphocytes, plasma cells, histiocytes, and associated fibrosis. The fourth patient demonstrated a lymphohistiocytic reaction with a predominance of histiocytic cells as well as associated plasma cells, fibroblasts, and fibrosis. The lymphoid infiltration in these reactions showed a predominance of T-lymphocytes over B-lymphocytes. Aluminum was demonstrated in necrotic foci, inflammatory stroma, and the granular cytoplasm of histiocytes with the aid of solochrome azurine and solochrome cyanine stains as well as by energy-dispersive x-ray microanalysis. The reactions are thought to be immunologic (hypersensitivity) reactions associated with the aluminum contents of the preparation.