Inclusion Criteria:  Hospitalized with COVID-19 confirmed per a positive PCR of any specimen (e.g., respiratory, blood, urine, stool, or other bodily fluid) and evidenced by chest x-ray or CT scan Receiving systemic corticosteroids at baseline Oxygen saturation < 93% on room air, or requiring supplemental oxygen, non-invasive or invasive mechanical ventilation, or extracorporeal membrane oxygenation (ECMO) to maintain oxygen saturation > 92% at screening and baseline  Exclusion Criteria:  Gestational age < 37 weeks Known severe allergic reactions to TCZ or other monoclonal antibodies Active tuberculosis infection Uncontrolled active bacterial, fungal, viral, or other infection (besides COVID-19) Diagnosis or suspected diagnosis of multisystem inflammatory syndrome in children (MIS-C) In the opinion of the investigator, progression to death is imminent and inevitable within the next 48 hours, irrespective of the provision of treatments Have received oral anti-rejection or immunomodulatory drugs (including TCZ) within the past 3 months prior to enrollment Treatment with an investigational drug within 5 drug-elimination half-lives or 30 days, whichever is longer, of enrollment (except for anti-SARS-CoV-2 antibodies or directly-acting antivirals) Participating in another interventional drug clinical trial (except for anti-SARS-CoV-2 antibodies or directly-acting antivirals)