My mother had GBS at the age of 66, but there was no vaccine involved. It was preceded by a lingering stomach virus. A friend's mother also had it in her early 60's, preceded by a viral infection. Kind of sobering to think you can get something that normally runs its course (the common cold, the flu, Norwalk, etc.), and end up paralyzed.
If Lucy is only complaining of weakness, they've caught it early. She's lucky, she will probably need PT but the GBS will not progress to the point where she is fully paralyzed or needs to be put on a respirator.
Have not reat this; but have you hear/read of Dr. Mary's Monkey? You can just google if interested. Incredible in it's premises and asertions and unfolding.