additive effect – The Multi-Regional Clinical Trials Center of Brigham and Women's Hospital and Harvard

additive effect additive effect

The combined effect when two or more things are used together.

Example of additive effect in a sentence

The additive effect of a combination drug is the sum of the effects of each drug acting alone.

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For example, two vaccines may be combined into one shot because they do not interfere with each other and will still each have the same effect as if they were given as two separate shots.

So an additive effect means that 1+1 = 2

Other info to think about when joining a study

You may hear the words “additive effect” being used if you are part of a study that is studying two or more treatments being taken together.

You may want to find out more about why the two treatments are being given together and what the hoped effect could be.

An illustration showing an example of additive effect like an equation. One type of topical cream for a red rash drawn in a circle reduces the size of the rash a bit and makes it less red. There is an addition sign to the right of that. Another type of topical cream for a rash has the same effect. When the two creams are used together, demonstrated to the left of a equal sign, the rash decreases in size by twice the amount as when the topical creams used individually.

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Version 2.0 September 2024

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