Is the cheese at Jersey Mike's vegetarian? Yes, it is!
Not all cheese is vegetarian. If you are a vegetarian you will want to ensure that the cheeses you eat are actually vegetarian. Cheese is made with enzymes, and the source of those enzymes determines if the cheese is vegetarian or not. If the source of the enzymes is microbial then the cheese is vegetarian. If the source of the enzymes is animal then the cheese is not vegetarian. This is because the animal is killed, and the enzymes are taken from the cow's stomach.
Some companies are good about letting you know if they use microbial or animal-sourced enzymes, but most don't offer the info. You have to go looking for it and ask them. Recently, I contacted Jersey Mike's sub shops to ask them about the source of the enzymes in their cheese. Here's the response I got in return:
"Regarding our cheeses, they are all made with microbial (plant based) enzymes. As far as our bread is concerned, the enzyme is part of the dough conditioner and does not contain any animal based ingredients. The enzyme is from microbial sources."
So, according to their information, the cheese and bread at Jersey Mike's is all vegetarian, as they use microbial sources. If you are new to Jersey Mike's, they do offer a couple of vegetarian options. They have a veggie sub, which comes with cheese and veggies, and they have a portabella mushroom and swiss sub.