* current standard of care treatments for covid-19 appear to be working and the subject is clinically improving * a previous stem cell infusion unrelated to this trial * certain medical conditions that pose a safety risk to the subject * pregnant or breast feeding or planning to during the study * suspected uncontrolled active bacterial, fungal, viral, or other infection * history of splenectomy, lung transplant, or lung lobectomy * concurrent participation in another clinical trial involving therapeutic interventions * expected survival or time to withdrawal of life-sustaining treatments expected to be \<7 days * has an existing "do not intubate" order * has undergone home mechanical ventilation (noninvasive ventilation or via tracheotomy) expect for continuous positive airway pressure or bi-level positive airway pressure (cpap/bipap) used solely for sleep-disordered breathing

* current standard of care treatments for covid-19 appear to be working and the subject is clinically improving * a previous stem cell infusion unrelated to this trial * certain medical conditions that pose a safety risk to the subject * pregnant or breast feeding or planning to during the study * suspected uncontrolled active bacterial, fungal, viral, or other infection * history of splenectomy, lung transplant, or lung lobectomy * concurrent participation in another clinical trial involving therapeutic interventions * expected survival or time to withdrawal of life-sustaining treatments expected to be \<7 days * has an existing "do not intubate" order * has undergone home mechanical ventilation (noninvasive ventilation or via tracheotomy) expect for continuous positive airway pressure or bi-level positive airway pressure (cpap/bipap) used solely for sleep-disordered breathing

- current standard of care treatments for covid-19 appear to be working and the subject is clinically improving - a previous stem cell infusion unrelated to this trial - certain medical conditions that pose a safety risk to the subject - pregnant or breast feeding or planning to during the study - suspected uncontrolled active bacterial, fungal, viral, or other infection - history of splenectomy, lung transplant, or lung lobectomy - concurrent participation in another clinical trial involving therapeutic interventions - expected survival or time to withdrawal of life-sustaining treatments expected to be <7 days - has an existing "do not intubate" order - has undergone home mechanical ventilation (noninvasive ventilation or via tracheotomy) expect for continuous positive airway pressure or bi-level positive airway pressure (cpap/bipap) used solely for sleep-disordered breathing

- current standard of care treatments for covid-19 appear to be working and the subject is clinically improving - a previous stem cell infusion unrelated to this trial - certain medical conditions that pose a safety risk to the subject - pregnant or breast feeding or planning to during the study - suspected uncontrolled active bacterial, fungal, viral, or other infection - history of splenectomy, lung transplant, or lung lobectomy - concurrent participation in another clinical trial involving therapeutic interventions - expected survival or time to withdrawal of life-sustaining treatments expected to be <7 days - has an existing "do not intubate" order - has undergone home mechanical ventilation (noninvasive ventilation or via tracheotomy) expect for continuous positive airway pressure or bi-level positive airway pressure (cpap/bipap) used solely for sleep-disordered breathing