With no hospitals or medical specialists in space, NASA and other space agencies have always been concerned about astronauts getting sick while on a mission. To minimize the chances of this, they usually spend the two weeks prior to launch in quarantine.
A Covid-19 superspreader event on the space station would disrupt operations.
The interior of the space station has a volume equivalent to a Boeing 747 jetliner, so infected crew members have room to isolate themselves. But space station managers certainly don't want to worry about the virus spreading in the station's constantly filtered and recycled air.
During a press conference last week, Shane Kimbrough, the NASA astronaut who is in command of Crew-2, said that all four astronauts had received Covid vaccinations. "I think it went well," he said. “We all have slightly different reactions, just like most people. So we're no different in this regard. But we are grateful that we have the vaccines. "
The three astronauts who launched a Soyuz rocket to the station earlier this month – Oleg Novitskiy and Pyotr Dubrov from the Russian space agency and Mark Vande Hei from NASA – were also vaccinated.
The four astronauts on the Crew 1 mission are not, as no vaccines were available when it launched last November. When they return to Earth, everyone who is not on the planet will be vaccinated against Covid-19.