This mattress protector may work fine, I don't know, I just got it. The reason I gave it only an average rating is because it is NOT all natural, as seems to be implied.
The waterproof backing is Polyurethane. I did not see anything in the description about any materials except bamboo. So I assumed it used a tightly woven bamboo fabric backing to make it waterproof. I used to use cotton diaper covers that were very effective, so it did not seem unusual to me that a natural fiber could be used for this purpose.
And I know there are organic cotton barrier covers that protect against dust mites, so I thought this would be the bamboo version of that product. The organic cotton ones are very expensive, so I thought I could still get something all natural only more affordable.
I guess I'll just keep it and use it until I can afford an organic cotton one. The lesson learned here is "you get what you pay for."