A modified Staphylococcal enterotoxin B (SEB) having resistance to a protease and a reduced toxicity and a vaccine comprising said modified SEB are provided. A modified SEB which has an amino acid sequence as set forth in SEQ ID NO: 1 wherein each of the lysine at 97-position and the lysine at 98-position are substituted with any other amino acid, or a derivative thereof and a vaccine comprising said modified SEB or a derivative thereof.
