Columbia had ejection seats for the four Orbital Flight Test missions
(STS-1 through 4) in 1981-82. The seats were still in place, but
deactivated for STS-5, and were removed shortly thereafter. The seats
were only available for the Commander and Pilot. After the loss of
Challenger, NASA considered many emergency egress systems, but
rejected most of them for cost and mass reasons. Only a jettison
mechanism for the hatch and a slide-pole were installed. This allows
astronauts to bail out of the Shuttle and not impact the wing on the
way out. However, this would only work in level, subsonic flight and
would not help the crew in a Challenger-like launch emergency.

See
Space Shuttle : The History of the National Space Transportation System : The First 100 Missions
by Dennis R. Jenkins

Alex R. Blackwell
University of Hawaii