It soon proved its efficacy, and redeemed the leech’s pledge.
Man had marked this woman’s sin by a scarlet letter, which had such potent and disastrous efficacy that no human sympathy could reach her, save it were sinful like herself.
It was impossible to doubt that, whatever painful efficacy there might be in the secret sting of remorse, a deadlier venom had been infused into it by the hand that proffered relief.
Souls, it is said, more souls than one, were brought to the truth by the efficacy of that sermon, and vowed within themselves to cherish a holy gratitude towards Mr. Dimmesdale throughout the long hereafter.
There are no more uses of "efficacy" in the book.
Show samples from other sources
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.