Of the 945 astronauts who flew the shuttle, only 1.4% perished the same failure rate as the shuttle!
Not too bad really, considering it's nearly 40 year old reusable tech.
(of course the % gets worse if you only count missions flown for each lost space craft).
Challenger was caused by a design flaw, which was rectified.
Columbia was a tragedy which could have been avoided if anybody had bothered to check from the ground, or commission a space walk. The carbon carbon panels were supposed to be indestructible, but obviously weren't.
The shuttle could have been saved by flying in with one side taking the brunt of the friction.
But we know what happened. It's terrible, but they all knew the risks.
Of all manned space flight, there are only 18 people who have died during a mission and 11 who have died during training.
That's 29 people for 295 manned flights to date (people per flight varies from 1-7 depending on launch vehicle).
530 people have flown in space to date.