Plagued by typhus on the Eastern Front, the German army turned to eccentric Polish zoologist Rudolf Weigl, who had developed a vaccine in the 1920s. But Wiegl, a devout Christian, was outraged by Nazi atrocities, and instead made his laboratory in Lviv a haven for refugee scientists. Using their protected status, they illegally sent the vaccine into Polish ghettos, while shipping weakened serum to the Wehrmacht. The author of Vaccine: The Controversial Story of Medicine's Greatest Lifesaver, Arthur Allen here pairs Weigl's story with that of one of his refugees, Jewish immunologist Ludwik Fleck, imprisoned at Buchenwald and offered a chance to save his own life by working for his captors.

"Allen is unflinching in his retelling of this monstrous era, but he manages to avoid writing a depressing narrative. Instead, Weigl, Fleck and their vaccines illuminate the inherent social complexities of science and truth and reinforce the overriding good of man. An unforgettable book."—Kirkus Reviews (starred review)