1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab and 2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available and/or 3. laboratory abnormalities such as C-reactive protein > 100 mg/L or D-dimer > 1000 ng/ml or IL-6 > 50 IU or suspected cytokine release syndrome (Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab and 2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available and/or 3. laboratory abnormalities such as C-reactive protein > 100 mg/L or D-dimer > 1000 ng/ml or IL-6 > 50 IU or suspected cytokine release syndrome (Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab and 2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available and/or 3. laboratory abnormalities such as C-reactive protein > 100 mg/L or D-dimer > 1000 ng/ml or IL-6 > 50 IU or suspected cytokine release syndrome (Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab and 2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available and/or 3. laboratory abnormalities such as C-reactive protein > 100 mg/L or D-dimer > 1000 ng/ml or IL-6 > 50 IU or suspected cytokine release syndrome (Criteria 1 and 2 are mandatory and 3 is optional)