If you look in the advair box, you will find a big sheet of paper with all the statistics for the warning.
I included some scans below. They don't conatin any different information than what was said here, but I thought you might want to see it for yourself. Basically, an average of 8 people died out of 10,000.
One other thing, is your son on the discus or the inhaler? The inhaler works much, much better than the discus.
<b>Edit:</b> On the larger picture, you have to expand it to read it properly. (hold the mouse on the picture, then wait for the little box in the lower-right corner to appear and click on it)