https://www.cbsnews.com/news/an-astronaut-medical-concern-prompts-nasa-to-delay-planned-spacewalk/

A spacewalk planned for Thursday outside the International Space Station was called off late Wednesday because of a "medical concern" with an unidentified crew member, NASA said in a statement.

While NASA did not identify the astronaut in question or explain the medical issue — standard practice due to privacy concerns — the agency said "the matter involved a single crew member who is stable."