I have heard that while no cases have been reported, there is the same risk of getting TSS as using tampons. I don't know why, and this seems to go against most of the things all over the web about menstrual cups. Their main point seems to be that this eliminates the risk of TSS. 
 However, I ordered one, and while it makes no mention of this on the website..the instructions that came with it said not to use if the wearer has ever had TSS in the past. 
 I wonder why that is? That put me off. I'll try contact the company and report back.