Male or female ≥16 years of age SARS-CoV-2infection (clinically suspected+ or laboratory confirmed*). Admitted to hospital as in-patient less than 96 hours prior to randomisation^ Illness of any duration, and at least one of the following: o Radiographic infiltrates by imaging (e.g. chest x-ray, computed tomography (CT) scan) OR o Evidence of rales/crackles on physical examination OR o Peripheral capillary oxygen saturation (SpO2) ≤94% on room air prior to randomization OR o Requiring supplemental oxygen. OR o Lymphocyte count <1 x 109 cells per litre (L) Participant (or legally authorized representative) provides written informed consent Able to take oral medication Participant (or legally authorised representative) understands and agrees to comply with planned trial procedures. *Laboratory-confirmed: SARS-CoV-2 infection as determined by polymerase chain reaction (PCR), or other commercial or public health assay in any specimen < 96 hours prior to randomization. +Clinically suspected: in general, SARS-CoV-2 infection should be suspected when a patient presents with (i) typical symptoms (e.g. influenza-like illness with fever and muscle pain, or respiratory illness with cough and shortness of breath), and (ii) compatible chest X-ray findings (consolidation or ground-glass shadowing), and (iii) alternative causes have been considered unlikely or excluded (e.g. heart failure, influenza). However, the diagnosis remains a clinical one based on the opinion of the managing doctor ^Where a patient has been admitted to hospital for a non COVID-19 reason and develops COVID-19 symptoms whilst an in-patient, randomisation my occur up to 96 hours from onset of symptoms.

Male or female ≥16 years of age SARS-CoV-2infection (clinically suspected+ or laboratory confirmed*). Admitted to hospital as in-patient less than 96 hours prior to randomisation^ Illness of any duration, and at least one of the following: o Radiographic infiltrates by imaging (e.g. chest x-ray, computed tomography (CT) scan) OR o Evidence of rales/crackles on physical examination OR o Peripheral capillary oxygen saturation (SpO2) ≤94% on room air prior to randomization OR o Requiring supplemental oxygen. OR o Lymphocyte count <1 x 109 cells per litre (L) Participant (or legally authorized representative) provides written informed consent Able to take oral medication Participant (or legally authorised representative) understands and agrees to comply with planned trial procedures. *Laboratory-confirmed: SARS-CoV-2 infection as determined by polymerase chain reaction (PCR), or other commercial or public health assay in any specimen < 96 hours prior to randomization. +Clinically suspected: in general, SARS-CoV-2 infection should be suspected when a patient presents with (i) typical symptoms (e.g. influenza-like illness with fever and muscle pain, or respiratory illness with cough and shortness of breath), and (ii) compatible chest X-ray findings (consolidation or ground-glass shadowing), and (iii) alternative causes have been considered unlikely or excluded (e.g. heart failure, influenza). However, the diagnosis remains a clinical one based on the opinion of the managing doctor ^Where a patient has been admitted to hospital for a non COVID-19 reason and develops COVID-19 symptoms whilst an in-patient, randomisation my occur up to 96 hours from onset of symptoms.