Two patient populations will be included in the study: (1) elderly and high COVID-age population and (2) high-risk immunocompromised population. (1) Elderly and high COVID-age population: 1. SARS-CoV-2 RNA detected in a specimen, ≤ 5 days after onset of symptoms 2. Symptoms of COVID-19 (so including but not limited to: fever, cough, breathlessness, chest pain, wheeze, sore throat, haemoptysis, runny nose, fatigue, muscle or joint pain, confusion, headache, seizures, nausea, vomiting, diarrhoea, abdominal pain, poor appetite, skin ulcers or rash, ear pain, conjunctivitis, anosmia, bleeding, lymphadenopathy.52 The attending clinician will determine if symptoms are consistent with COVID-19. 3. Clinical status not requiring admission to hospital for COVID-19 disease and oxygen support 4. Ability to transfuse (per randomisation) within 5 days after onset of symptoms 5. Men or women, 70 years or older OR under 70 years with significant comorbidities (arterial hypertension, diabetes, obesity, asthma or other chronic pulmonary disease, cardiovascular disease, cerebrovascular disease, chronic kidney disease / dialysis, hemoglobinopathies, liver disease, chronic neurological disease, rheumatoid arthritis, lupus or psoriasis) resulting in a ‘COVID-age’ of 70 years or more according to the ALAMA risk calculator https://alama.org.uk/covid-19-medical-risk-assessment/ 6. Signed written informed consent (2) High-risk immunocompromised population 1. SARS-CoV-2 RNA detected in a specimen, ≤ 5 days after onset of symptoms 2. Symptoms of COVID-19 (so including but not limited to: fever, cough, breathlessness, chest pain, wheeze, sore throat, haemoptysis, runny nose, fatigue, muscle or joint pain, confusion, headache, seizures, nausea, vomiting, diarrhoea, abdominal pain, poor appetite, skin ulcers or rash, ear pain, conjunctivitis, anosmia, bleeding, lymphadenopathy.52 The attending clinician will determine if symptoms are consistent with COVID-19. 3. Clinical status not requiring admission to hospital for COVID-19 disease and oxygen support 4. Ability to transfuse (per randomisation) within 5 days after onset of symptoms 5. Male or female Adult ≥18 years of age with extremely high risk including: a. Patients with at least one of the following acquired immune deficiencies: i. Lymphoid malignancies treated within the last 12 months ii. Lymphoid malignancies with persistent hypogammaglobulinaemia (IgG < 5 g/L) iii. Myeloid malignancies treated by chemotherapy within the last 12 months iv. Myeloid malignancies treated with anti-BCL-2 drugs within the last 12 months v. Myeloid malignancies associated with prolonged neutropenia (≥ 6 weeks) vi. Solid tumour undergoing treatment with chemotherapy (until 3 months after completion of the last chemotherapy cycle). vii. Allogenic hematopoietic stem cell transplantation within the last 12 months or anytime if on-going treatment for chronic GVHD viii. Organ transplantation ix. Anti - B (CD20/CD19) MoAb and/or mycophenolate mofetil treatment within the last 12 months x. Anti-CD19/CD20 CAR-T cell treatment xi. ATG or alemtuzumab treatment within the last 6 months xii. AIDS or b. Patients with primary lymphoid immune deficiencies: i. B cell deficiencies (such as Bruton agammaglobulinemia) ii. T cell deficiencies (such as Wiskott Aldrich disease) iii. Combined deficiencies (such as Common variable immunodeficiency ) or c. Patients without detectable seroconversion ≥ 3 weeks after complete vaccination schedule with an approved vaccine. 6. Signed written informed consent

Two patient populations will be included in the study: (1) elderly and high COVID-age population and (2) high-risk immunocompromised population. (1) Elderly and high COVID-age population: 1. SARS-CoV-2 RNA detected in a specimen, ≤ 5 days after onset of symptoms 2. Symptoms of COVID-19 (so including but not limited to: fever, cough, breathlessness, chest pain, wheeze, sore throat, haemoptysis, runny nose, fatigue, muscle or joint pain, confusion, headache, seizures, nausea, vomiting, diarrhoea, abdominal pain, poor appetite, skin ulcers or rash, ear pain, conjunctivitis, anosmia, bleeding, lymphadenopathy.52 The attending clinician will determine if symptoms are consistent with COVID-19. 3. Clinical status not requiring admission to hospital for COVID-19 disease and oxygen support 4. Ability to transfuse (per randomisation) within 5 days after onset of symptoms 5. Men or women, 70 years or older OR under 70 years with significant comorbidities (arterial hypertension, diabetes, obesity, asthma or other chronic pulmonary disease, cardiovascular disease, cerebrovascular disease, chronic kidney disease / dialysis, hemoglobinopathies, liver disease, chronic neurological disease, rheumatoid arthritis, lupus or psoriasis) resulting in a ‘COVID-age’ of 70 years or more according to the ALAMA risk calculator https://alama.org.uk/covid-19-medical-risk-assessment/ 6. Signed written informed consent (2) High-risk immunocompromised population 1. SARS-CoV-2 RNA detected in a specimen, ≤ 5 days after onset of symptoms 2. Symptoms of COVID-19 (so including but not limited to: fever, cough, breathlessness, chest pain, wheeze, sore throat, haemoptysis, runny nose, fatigue, muscle or joint pain, confusion, headache, seizures, nausea, vomiting, diarrhoea, abdominal pain, poor appetite, skin ulcers or rash, ear pain, conjunctivitis, anosmia, bleeding, lymphadenopathy.52 The attending clinician will determine if symptoms are consistent with COVID-19. 3. Clinical status not requiring admission to hospital for COVID-19 disease and oxygen support 4. Ability to transfuse (per randomisation) within 5 days after onset of symptoms 5. Male or female Adult ≥18 years of age with extremely high risk including: a. Patients with at least one of the following acquired immune deficiencies: i. Lymphoid malignancies treated within the last 12 months ii. Lymphoid malignancies with persistent hypogammaglobulinaemia (IgG < 5 g/L) iii. Myeloid malignancies treated by chemotherapy within the last 12 months iv. Myeloid malignancies treated with anti-BCL-2 drugs within the last 12 months v. Myeloid malignancies associated with prolonged neutropenia (≥ 6 weeks) vi. Solid tumour undergoing treatment with chemotherapy (until 3 months after completion of the last chemotherapy cycle). vii. Allogenic hematopoietic stem cell transplantation within the last 12 months or anytime if on-going treatment for chronic GVHD viii. Organ transplantation ix. Anti - B (CD20/CD19) MoAb and/or mycophenolate mofetil treatment within the last 12 months x. Anti-CD19/CD20 CAR-T cell treatment xi. ATG or alemtuzumab treatment within the last 6 months xii. AIDS or b. Patients with primary lymphoid immune deficiencies: i. B cell deficiencies (such as Bruton agammaglobulinemia) ii. T cell deficiencies (such as Wiskott Aldrich disease) iii. Combined deficiencies (such as Common variable immunodeficiency ) or c. Patients without detectable seroconversion ≥ 3 weeks after complete vaccination schedule with an approved vaccine. 6. Signed written informed consent