Move oven rack to low position so that tops of pans will be in center of oven. Heat oven to 350ºF. Grease bottoms only of 2 loaf pans, 8 1/2x4 1/2x2 1/2 or 9x5x3 inches.
In large bowl, beat butter and sugar with electric mixer on medium speed until blended. Stir in eggs until well blended. Add bananas, sour cream and vanilla. Beat until smooth. Stir in flour, baking soda and salt just until moistened. Stir in blueberries.
Pour into pans.
Bake 1 hour to 1 hour 10 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes. Loosen sides of loaves from pans; remove from pans. Cool completely on wire rack before slicing. Wrap tightly and store in refrigerator up to 1 week.