A Study to Evaluate the Efficacy and Safety of Tocilizumab in Hospitalized Participants With COVID-19 Pneumonia

Inclusion Criteria * Hospitalized * COVID-19 pneumonia confirmed by a positive polymerase chain reaction (PCR) of any specimen and radiographic imaging * SpO2 \< 94% while on ambient air Inclusion Criteria Specific to Long-Term Extension * Participated in Study ML42528 (EMPACTA) (includes participants who completed or discontinued early from the main study) Exclusion Criteria * Known severe allergic reactions to TCZ or other monoclonal antibodies * Require continuous positive airway pressure (CPAP), bilevel positive airway pressure (BIPAP), or invasive mechanical ventilation * Suspected active bacterial, fungal, viral, or other infection (besides COVID-19) * In the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments * Immunocompromised (besides well-controlled HIV) or on immunosuppressive therapy (except for steroids for COVID), advanced cancer * Have received oral anti-rejection or immunomodulatory drugs (including TCZ) within the past 3 months * Participating in another interleukin (IL)-6 antagonist clinical trial or other drug clinical trials (participation in COVID-19 anti-viral trials may be permitted if approved by Medical Monitor) * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 10 x upper limit of normal (ULN) detected within 24 hours at screening (according to local laboratory reference ranges) * Absolute neutrophil count (ANC) \< 1000/uL at screening (according to local laboratory reference ranges) * Platelet count \< 50,000/uL at screening (according to local laboratory reference ranges) * Pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination * Treatment with an investigational drug within 5 half lives or 30 days (whichever is longer) of randomization (investigational COVID-19 antivirals may be permitted if approved by Medical Monitor) * Any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study * Any history of Diverticulitis or GI perforation * Use of systemic corticosteroids unless on a stable chronic dose