There are three kinds of people: the haves, the have-nots, and the have-not-paid-for-what-they-haves."
Earl Wilson
The impact of QE
When central banks buy Treasury debt, central bank reserves grow and, when that happens, base money supply increases. Money supply is an important driver of economic growth; hence, it is fair to say that economic activity not only benefits from the fall in interest rates that typically comes with QE; it also benefits from the increase in money supply.
Having said that, when money supply grows rapidly, inflation often follows. With the dramatic increase in QE