Nope! I've got the American Tourister ones and you pack it full of stuff, close it like a zip-loc, and roll the air out the bottom. There's a little air passage that lets air out but not back in.
I've managed to pack 6 dresses, 4 skirts, and 4 shirts into one, and shrink it down into something no bigger than a small pillow. Amazing, and highly recommended from me!