Paul Ewald’s Plague Time includes this example of lost progress:
In 1874, eight years before Robert Koch presented his discovery of the bacterial agents that cause tuberculosis, a lesser-known microbe hunter, Arthur Boettcher, published a paper on a small, curved bacterium that he found repeatedly in ulcers of the stomach. Over the next half century, several other scientists confirmed Boettcher’s finding. Some also extended the research by experimentally transmitting the bacterium in lab animals. By the late 1940s peptic ulcers were being successfully treated with antibiotics in New York City hospitals.
Paul Fremont-Smith was a young intern in 1948 at Manhattan’s New York Hospital. He remembers the orders he was given there by his no-nonsense supervisor, Connie Guion. She told him, “The people over at Mount Sinai have found that Aureomycin [a trade name for chlortetracycline] is effective against peptic ulcers. Use it. It works.” He did, and it worked. Then, around 1950, discussions of infectious causation of ulcers disappeared from the literature and from the treatment regimen. The medical texts from 1950 through the early 1990s attributed peptic ulcers to gastric acidity, stress, smoking, alcohol consumption, and genetic predispositions — everything but infection. Generally there was not even a reference to the possibility of infectious causation.