MIX milk, sugar, tapioca and egg in medium saucepan. Let stand 5 min. COOK on medium heat until mixture comes to full boil, stirring constantly. Remove from heat. Stir in vanilla. Cool 20 min.; stir. Serve warm or chilled. (Pudding thickens as it cools. For creamier pudding, place plastic wrap on surface of pudding while cooling. Stir before serving.) Store leftovers in refrigerator.