We use the standard vinyl mattress covers and don't consider them to be a problem. But for us, the more important consideration is adequate diapering. The mattress cover is only a "just-in-case" form of extra protection, because my diapers don't leak. It was important to me to protect my wife from being subjected to having to wake up in wet sheets because of my bedwetting. Contrary to what some people say, it IS possible to prevent diapers from leaking. I wear pinned cloth diapers and rubber pants, but in between them I also wear an "all in one" terry-lined waterproof nylon diaper with the wrap-around wings that fasten with velcro in front. Contrary to the manufacturers claims, these garments are almost totally worthless if you try to use it as protection by itself. But in combination with other things, they can increase the protection to the point that full security is achieved. I sleep on my side frequently. With enough thickness, proper folding of my diapers so I have adequate absorbency on the sides as well as everywhere else, and properly fitting plastic or rubber pants, I am able to keep my wife dry and experience the pleasure of waking up in a completely dry bed.