Clinical Research Glossary

efficacy efficacy


How well a study treatment works in the study.

Example of efficacy in a sentence

A study tests efficacy to see how well a new treatment works.

More Info

Efficacy is different from “effectiveness” which refers to how well the treatment works in the real world outside a study.

Other info to think about when joining a study

The word “efficacy” can be used to describe how well the investigational intervention works in the controlled setting of a study.

This term may be used when researchers describe an objective in the study.
For example, a study could be testing the efficacy of a new vaccine.

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