• Laboratory confirmed SARS-CoV-2 infection by RT-PCR or positive antigenic test

• Asymptomatic or mild to moderate COVID-19 (WHO progression scale \<5). Patients receiving oxygen therapy for reasons other than a pulmonary COVID-19 are eligible)

• ≥ 16 years of age;

• Immunocompromised as defined by ≥ 1 risk factors for severe COVID-19 as assessed by the FOPH list (criteria 5: diseases/treatments leading to immune suppression)

‣ Severe immunosuppression (e.g., HIV infection with CD4 + T cell count \<350 / µl)

⁃ Neutropenia (\<1000 neutrophils / µl) ≥1 week

⁃ Lymphocytopenia (\<200 lymphocytes/µl)

⁃ Hereditary immunodeficiencies

⁃ Intake of drugs which suppress the immune system (e.g. glucocorticoids for a long time \[an equivalent dose of prednisone \>20 mg/day \> 3 months\], monoclonal antibodies, cytostatics, biological products, everolimus, mTOR inhibitors etc.) in the last 12 months

⁃ Active cancer under cytostatics or targeted therapy known to be immunosuppressive (e.g., platinum salts, cyclophosphamide, anthracyclines, taxanes, 5-fluorouracil, gemcitabine, purine inhibitors, proteasome inhibitors) or associated with hematologic toxicity (neutropenia, lymphopenia), for example sunitinib, imatinib, regorafenib

⁃ Aggressive lymphomas (all types)

⁃ Acute lymphatic leukemia

⁃ Acute myeloid leukemia

⁃ Acute promyelocytic leukemia

⁃ T prolymphocytic leukemia

⁃ Primary central nervous system lymphoma

⁃ Stem cell transplantation

⁃ Light chain amyloidosis

⁃ Chronic lymphoid leukemia

⁃ Multiple myeloma

⁃ Sickle cell disease

⁃ Bone marrow transplant

⁃ Organ transplant

⁃ Being on the waiting list for an organ transplant

• Willing and able to comply with study requirements and restrictions as described in the informed consent form (ICF)

• Enrolled in or a beneficiary of a Social Security program (State Medical Aid (AME) is not a Social Security program) or holders of health insurance

• Participant's or its legal representative's signature of the informed consent form