This is exactly what Olav Mella said to me as I sat next to him at a tea break at the IiME conference in May this year. Yes it really is that sort of conference: patients and carers have a chance to talk to speakers and other professionals.
He was clear that there would be no unblinding until the end of the trial. I did ask what would happen if they noticed that many participants were getting sig better, but his answer was the same.
I said that I realised 2 or 3 years was not long in terms of research, but that for youngsters (or really anyone else whose life is derailed by this disease) it's an eternity.