Every four months, pathologist Aaron LeBeau scoops into a net one of the five nurse sharks he keeps in his University of Wisconsin lab. Then he carefully administers a shot to the animal, much like a pediatrician giving a kid a vaccine. The shot will immunize the shark against human cancer, perhaps, or an infectious disease, such as Covid-19. A couple of weeks later, after the animal’s immune system has had time to react, LeBeau collects a small vial of shark blood.
