PROBLEM TO BE SOLVED: To provide a method for immediately inducing an immune response against an infectious agent such as smallpox and Bacillus anthracis.SOLUTION: A method comprises administering, to e.g. animals intravenously, intranasally, intramuscularly, or subcutaneously, an immunogenic composition comprising an inactivated poxvirus, preferably modified vaccinia virus Ankara (MVA), between 36 hours prior to infection with the infectious agent and 72 hours after infection with the infectious agent.SELECTED DRAWING: Figure 1【課題】痘瘡や炭疽菌等の感染性因子に対する免疫応答を即時に誘導するための方法の提供。【解決手段】不活化したポックスウイルス、好ましくは組換えワクシニアウイルス・アンカラ(MVA)を含む免疫原性組成物を、感染性因子による感染の36時間前から感染性因子による感染の72時間後までの間に、例えば動物の静脈内、鼻腔内、筋肉内、皮下に投与する方法。【選択図】図1