What are the chances of getting a tapeworm from a beef steak that may have been undercooked. (reddish inside)

Nearly zero: Tapeworm infection can be caused by eating raw or undercooked meat of infected animals, pork more common than beef. Usually there are no symptoms, perhaps a little abdominal discomfort; people see worms in stool! In the US, laws on feeding practices and the inspection of domestic food animal have largely eliminated tapeworms. Cook whole cut meat/steak to 145 and ground meat to 160. Stay well:)