ETHICS APPROVAL
This study was approved by the Ethics Committee for Human Research, Chulabhorn Research Institute (EC No. 192/2564). All severe COVID-19 patients were informed about the treatment, and all patients had written the consent forms before admission to receive all treatment options that might benefit all severe COVID-19 patients in addition to a standard of care during the outbreak. Specific CCP consent was not applicable. Our study followed the Helsinki Declaration of 1964 and its later amendments. Consent for publication was not applicable.