From Taco Bell Website:
Are there any items on your menu that are prepared without meat?
A: Several Taco Bell items do not include meat as an ingredient. Popular ones include the classic Bean Burrito, 1/2 lb. Bean Burrito Especial, 7-Layer Burrito, and Cheesy Fiesta Potatoes side item (the last two feature sour cream, which contains a very small amount of gelatin which is naturally animal-based). Of course you can also request that any item on the menu be prepared without meat or sour cream. The enzymes used in the production of our cheese, tortillas, and flatbread are not from an animal source.