Preheat oven to 375°F (190°C). Line a muffin tin with paper liners or spray lightly with oil.
In a bowl, whisk together egg, yogurt, applesauce, sugar, and vanilla.
In another bowl, mix flour, baking powder, baking soda, and salt.
Add dry ingredients to wet and stir until just combined (do not overmix).
Fold in blueberries gently.
Divide batter evenly into muffin cups, filling ¾ full.
Bake 18–22 minutes until tops are golden and a toothpick comes out clean.
Let muffins cool 5 minutes in the pan before transferring to a rack.