PROBLEM TO BE SOLVED: To provide vaccines or antibodies for delaying the onset of or treating Alzheimer's disease or Alzheimer-related disorders.SOLUTION: Disclosed herein is a vaccine that comprises a therapeutically effective amount of a physiologically acceptable protofibril/oligomer comprising N-terminal truncated amyloid β protein (Aβ). Also disclosed is an antibody that binds to one or more truncated Aβ protofibrils/oligomers but exhibits no or substantially no cross-reactivity with full-length Aβ monomers, and may optionally exhibit cross-reactivity to N-terminal truncated Aβ monomers. A method for detecting a soluble N-terminal truncated Aβ protofibril/oligomer and N-terminal truncated Aβ monomer using the antibody is also disclosed.SELECTED DRAWING: None【課題】アルツハイマー病又はアルツハイマー関連障害の発症を遅延させる又は治療するためのワクチン又は抗体の提供。【解決手段】N末端切断型アミロイドβタンパク質(Aβ)を含む、生理的に許容されるプロトフィブリル/オリゴマーの治療有効量を含有するワクチン。1又はそれ以上の切断型Aβプロトフィブリル/オリゴマーに結合するが、完全長Aβモノマーとは交差反応性を示さないか又は実質的に交差反応性を示さず、場合によりN末端切断型Aβモノマーに交差反応性を示す、抗体。前記抗体を使用する、可溶性N末端切断型Aβプロトフィブリル/オリゴマー及びN末端切断型Aβモノマーの検出方法。【選択図】なし