I've been making this soup for years. It is a favorite in our household.
Sometimes I substitute ham or a ham bone for the bacon. Other times, I use both ham and bacon. And if I have neither in the house, it's delicious without. Just substitute olive oil for the 2Tbs. of bacon fat and sprinkle each bowl of soup with grated cheese (my family prefers pecorino romano but parmesan is good, too.)