*2.1. Study Population, Setting, and Clinical Data*

The study population consists of consecutive adult LTR recipients ≥18 year of age with COVID-19 at the University Hospital Zurich, Switzerland, in which formal informed consent was given. No patient had to be excluded due to lack of informed consent or age <18 years. For the diagnosis of COVID-19, a laboratory confirmation of SARS CoV-2 by real time reverse transcriptase polymerase chain reaction (RT-PCR) was required, irrespective of clinical signs and symptoms. The data comprised demographics, clinical, laboratory and radiology characteristics as well as treatments and outcomes. The data were abstracted from the electronic medical record of the patients. The long-term immunosuppression was recorded. We also documented comorbidity including hypertension, diabetes, cardiovascular disease, malignancy and chronic kidney disease.

Severity of disease was classified according to Siddiqi [5]. The risk stratification by the AIFELL score was documented [6]. Data on antiviral, antibiotic and anti-inflammatory therapy were recorded, as well as clinical treatment setting (normal ward, intermediate care, and intensive care). Additionally, we recorded the need for oxygen therapy (normal breathing without additional oxygen, oxygen therapy with nasal cannula, non-rebreather face mask, high flow oxygen therapy, non-invasive ventilation, invasive mechanical ventilation or extracorporeal membrane oxygenation). Full recovery was defined as two negative SARS CoV-2 RT-PCR tests at least 24 h apart along with resolution of symptoms and clinical syndrome, and in case of hospital discharge without the need for additional oxygen therapy.

#### *2.2. Laboratory and Radiology Assessment*

Diagnosis of COVID-19 was confirmed by RT-PCR using nasopharyngeal swabs. Laboratory investigations included complete blood count (hemoglobin, leucocytes and platelets) with differential blood count including eosinophils, neutrophils, and lymphocytes. The chemistry panel included the renal function, liver enzymes, and the C-reactive protein (CRP). Radiology data included computed tomography (CT) scan of chest in all hospitalized patients.
