Elizabeth had nothing to propose of deeper efficacy.
Captain Benwick listened attentively, and seemed grateful for the interest implied; and though with a shake of the head, and sighs which declared his little faith in the efficacy of any books on grief like his, noted down the names of those she recommended, and promised to procure and read them.
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.