Strictly speaking, this isn't a standard QE this time, as there's no real balance sheet expansion. However, with a scale of $40 billion, liquidity has indeed been genuinely injected. The Fed itself is calling the "market water shortage," so this move at least added some water to the pond. How effective will it be? At the very least, it won't be worse than now, and it could temporarily ease some of the liquidity tightness.