Dr. Peter Hotez has always been fascinated by the kind of grisly afflictions that turn most people’s stomachs. As a 13-year-old, he spent hours poring over the authoritative tome Manson’s Tropical Diseases, keeping it within easy reach on his nightstand. He chose to spend his career studying hookworms—tiny, half-inch-long parasites that burrow into victims’ bodies and literally suck the life out of them. By the mid-1990s, Hotez’s research had reached a breakthrough: a concept for a vaccine to fight against the nasty tropical disease.

Hotez made the rounds at pharmaceutical firms, looking for a drug company to test his vaccine. But doors slammed in his face. He talked to animal health companies, makers of flea collars and sheep disinfectants, because hookworm also infests livestock. They turned him down, too. Having exhausted the traditional options, he wondered if he had hit the end of the road. “It was pathetic,” Hotez sighs. “Really discouraging.” He considered moving to Iowa to become a...