In 1989, Hotez moved to Yale University, where he conducted most of the early scientific work aimed at identifying a vaccine target. His early epidemiologic studies in China had revealed a wide variation in the number of worms among people who were routinely exposed to the parasite. He also knew from his early days as a graduate student that an attenuated larvae vaccine for canine hookworm had been developed in the 1960s and 1970s. Its manufacturer discontinued making it in 1975 after only a few years on the market, citing poor sales. Veterinarians, it turned out, made more money from routine deworming than from a one-time vaccine. Plus, some pet owners complained because they still saw worm eggs in their dogs' feces. To Hotez, though, the partial response suggested that some naturally occurring antibody, albeit stronger in some hosts than in others, was offering partial immunity.
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