Not much hope, but the medical community has a better track record of delivering results than praying.
??? Non-sequitur ???
Apparently one may use embryonic stem cells or adult stem cells (broad brush, from a layperson w.r.t. that field).
From the little I have read on FR, adult stem cell therapies are much more effective than embryonic -- hence the flood of demands that the government fund embryonic stem cell research, like the one in California for $6 billion or so...the thinking being (endorsed by libertarians and Free Market Types alike) is that if the treatment regime showed promise, then *private* money would flood in, in the hopes of exploiting the breakthrough for cash, and so government funding would be unnecessary.
Why you happened to compare this to prayer is unclear to me.
However, since you mentioned prayer, you need to do an apples to apples comparison: prayer is not mechanistic, as it is by definition a *request*. And the circumstances and/or conditions under which it will be answered are not known in advance, making every prayer a "double-blind" in a sense. Of course, given that in one town Jesus was unable to do many mighty works "because of their unbelief" it looks like any attempt to systematically study prayer by a true double-blind test may run into methodological errors: all of the participants may be unaware of the study, or to which group they are assigned, but God (to whom the prayers are addressed by the participants) is : and furthermore, He is aware of the study, and the purpose of the study.
Incidentally, have you considered the idea that God expects us to exercise some effort and/work on our own behalf: we pray "Give us this day our daily bread" but we are still expected to go to work, go to the store, buy, and cook the food. A similar expectation holds with regard to medicine and/or miracles: we should do the ordinary, and be prepared to set aside our pride enough to ask God for the *extra*ordinary.
One other point -- how did George Washington die? It was the best available medical science, wasn't it? Bleeding? And how about the "prudent diet" including margarine and high carbohydrates?
If you want to bleat about the "self-correcting nature of science" (and therefore put your thumb on the scale, by implicitly accepting only the elements of science which have been proven by hindsight), go ahead. But then for a fair comparison, you'd need to have Jesus, Elijah, Moses, and St. Paul doing the miracles for comparison. Good luck with that one.
Cheers!
...oh, and Merry Christmas.