Clinical Research Glossary

effectiveness effectiveness


How well a treatment works.

Example of effectiveness in a sentence

Effectiveness refers to how well a treatment, medicine, or vaccine works in people who use it after it has been approved.

More Info

Effectiveness refers to how well a treatment works in the real world, not in a planned clinical trial. Usually effectiveness is assessed after approval by health or government authorities.

Other info to think about when joining a study

The word “effectiveness” commonly comes up in the context of already approved medications.

In contrast, “efficacy” refers to how well a study treatment works in a study.

The words “effectiveness” and “efficacy” are sometimes used to mean the same thing even though they have slightly different meanings.

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