Hand Foot & Mouth Disease is a highly contagious virus that you most likely will encounter in your child's young lifetime.
Depending on the severity of the sores on the feet, bracing often can be continued, because the sores are not very severe. Do consider your child's severity for if to continue bracing. But, also, don't stop bracing for something that is not an issue. Many HFM kids do perfectly fine bracing through the illness with minor sores. As other illnesses do also come and go. Bracing is baby's normal. Disrupting that disrupts their day to day and difficulties arise.
It's us parents who feel like bracing is an issue, while kiddo feels like bracing is their normal. Not bracing is all about the parents not wanting to brace. When in sickness, the brace isn't going to cause discomfort, it's the sickness that causes that. Don't discard the brace to make kiddo comfortable. Their comfortable is with the brace ON.