efficacy
n. US //ˈɛfɪˌkæsi// UK //ˈɛfɪkəsi// ef·fi·ca·cy
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1 medical/scientific performance (n.) C1 Advanced Technical Academic Medicinehow well a drug or treatment works in a perfect, controlled test.
the performance of an intervention under ideal and controlled circumstances, such as a clinical trial. Often contrasted with 'effectiveness', which describes performance in real-world settings.
ExampleScientists are still testing the efficacy of the new vaccine against different viruses.
ExampleThe phase-three clinical trials demonstrated high efficacy in controlled environments, though researchers remain cautious about real-world effectiveness across diverse populations.
UsageFrequently used in the phrase 'clinical efficacy'.
From Old French efficace, from Late Latin efficācia (“efficacy”), from efficāx (“efficacious”); see efficacious.