LEIPZIG, GERMANY - AUGUST 22: Participants wearing FFP2 protective face masks take part in the RESTART-19 Covid transmission risk assessment study in a concert setting during a break for concessions at an indoor arena during the coronavirus pandemic on August 22, 2020 in Leipzig, Germany. The study, organized by the University Hospital of Halle (Saale), simulates a live concert venue with several thousand audience members in three different scenarios in order to develop risk reduction measures for large events. Participants wear tracer devices to track their movements and sensors measure aerosol currents in the arena. All participants had to undergo a Covid-19 test within the last 48 hours and test negative in order to take part. (Photo by Sean Gallup/Getty Images)