The evil side of my nature, to which I had now transferred the stamping efficacy, was less robust and less developed than the good which I had just deposed.
You will learn from Poole how I have had London ransacked; it was in vain; and I am now persuaded that my first supply was impure, and that it was that unknown impurity which lent efficacy to the draught.
There are no more uses of "efficacy" in the book.
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The doctor weighed the efficacy of each treatment against potential side-effects.
They held hearings to investigate concerns about the safety and efficacy of the vaccine.