German states set their respective regulations around events related to the COVID pandemic.
In accordance, GCS participants will have to be either fully vaccinated or recovered from COVID19. They have to prove this through documentation like the Digital EU Vaccination Certificate.
Attendance is not possible for people who are not fully vaccinated or recovered.
The German government recognizes the vaccines that are approved for use by the European Medicines Agency (EMA) - you find their list here: www.ema.europa.eu