In small bowl, stir together flour, poppy seeds, salt and baking soda. In large bowl, cream together sugar and butter. Beat in eggs, one at a time.
Beat in yogurt and vanilla til well blended. Stir in flour mixture til moistened thoroughly. Spoon batter into greased muffin tins and bake at 400 for 15 to 20 minutes or til a wooden pick inserted in center comes out clean. Cool muffins on wire rack for 5 minutes before serving.