PROBLEM TO BE SOLVED: To provide a highly-safe pharmacological composition capable of preventing effectively nocardiosis in cultivation of fishes such as young yellowtails or adult yellowtails, and a vaccine for fishes including the pharmacological composition, and to provide a simple and inexpensive method for producing the pharmacological composition.SOLUTION: A method for producing a pharmacological composition includes a culture step for culturing Nocardiaseriolae on a medium including a divalent cation chelating agent. A pharmacological composition obtained by a production method of the pharmacological composition, and a vaccine for fishes including the pharmacological composition are also provided.【課題】ハマチやブリなどの魚類の養殖におけるノカルジア症を効果的に予防することができる安全性の高い薬理組成物及び該薬理組成物を含有する魚類用ワクチン、並びに、前記薬理組成物の安価で簡便な製造方法の提供。【解決手段】２価カチオンキレート剤を含む培地でノカルジア・セリオレ（Ｎｏｃａｒｄｉａｓｅｒｉｏｌａｅ）を培養する培養工程を含む薬理組成物の製造方法、並びに、前記薬理組成物の製造方法により得られる薬理組成物、及び前記薬理組成物を含有する魚類用ワクチンである。【選択図】図１
