Little is known about the so-called post-Covid syndrome (PCS). A generally accepted definition of long-term Covid does not yet exist. Nivel used different definitions for its research, looking at the complaints that patients themselves reported, the patient data after a visit to the GP, the number of consultations and the amount of complaints. Depending on the definition used by Nivel, 20 to 37 percent of people with a corona infection had long-term complaints.