1. SARS-CoV-2 infection confirmed by PCR test 2. Hospitalised patients 3. WHO score 4-6 [28] 4. Oxygen saturation ≤ 92% under room air 5. Breathing frequency per minute ≥ 20 6. Patients ≥ 18 years and < 75 years 7. Written informed consent obtained prior to the initiation of any protocol-required procedures by the patient 8. Willingness to comply to study procedures and study protocol 9. Patients able to understand the requirements of the study and give written informed consent

1. SARS-CoV-2 infection confirmed by PCR test 2. Hospitalised patients 3. WHO score 4-6 [28] 4. Oxygen saturation ≤ 92% under room air 5. Breathing frequency per minute ≥ 20 6. Patients ≥ 18 years and < 75 years 7. Written informed consent obtained prior to the initiation of any protocol-required procedures by the patient 8. Willingness to comply to study procedures and study protocol 9. Patients able to understand the requirements of the study and give written informed consent