Baseline characteristics of the validation cohort
The cohort comprised 26 convalescent COVID-19 patients and 14 healthy donors as a control group. The median age of the COVID-19 patients at the time of study inclusion was 59 years, with participants ranging from 27 to 88 years of age. Subjects were of mixed gender with a higher percentage of males (58 %) than females (42 %). COVID-19 patients were included at a median time of 48 days after diagnosis or onset of symptoms (range 15-214). Eighteen patients had mild COVID-19 that did not require hospitalization, and they did not receive specific COVID-19 treatment. Five patients had moderate disease, of whom two were hospitalized and one received treatment with antibiotics and remdesivir. Three patients had severe disease, were hospitalized and received antibiotic treatment. All included patients were confirmed to be SARS-CoV-2 positive by RT-PCR and/or serological testing. Healthy volunteers (median age 48, range 26-60) were significantly younger than COVID-19 patients (median 59, range 27-88) (P =0.0323, two-tailed unpaired t-test). There were no significant differences regarding gender between COVID-19 patients and the control group (P =0.5024, Fisher’s exact test). Baseline characteristics are provided in Table 3.