Does anyone know the difference between efficacy and efficiency? I have seen the word efficacy used a lot recently but am not sure of its meaning.
I’d be grateful for the help, thanks!

An efficiency is a measure of effectiveness.  An efficacy is something that tastes effing great.

Short of effindelicacy?

Efficacy and efficiency are nearly synonymous. However, efficacy means capable of producing a result, whereas efficiency usually describes an action.

A drug has efficacy. In fact, efficacy is typically used in discussing drugs and medical treatment.
A person can work with efficiency. A machine can operate with efficiency.

...but what are its effects????

Huge profits for the drug companies.

That is all it is for every company: huge profits.

Bonuses have to come from somewhere.

To the tune of millions, I know.  Such a country. Very discouraging, if you let it get to you.