A Study to Investigate Intravenous Tocilizumab in Participants With Moderate to Severe COVID-19 Pneumonia

Inclusion Criteria * Hospitalization with COVID-19 pneumonia confirmed by a positive polymerase chain reaction (PCR) of any specimen \[e.g., respiratory, blood, urine, stool, and other bodily fluids\]) and evidence of pneumonia on chest X-ray or computed tomography scan * For severe patients, SpO2 \</= 93% or PaO2/FiO2 \< 300 mmHg. If a participant is on supplemental oxygen with SpO2 \> 93%, but desaturation \</= to 93% on lower supplemental oxygen or ambient air is documented during screening, the inclusion criterion is met * For moderate patients (those who do not qualify as severe based oxygen requirements), CRP \> 2 x upper limit of normal (ULN) is required * For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception, as defined by the protocol * For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use a condom, and agreement to refrain from donating sperm, as defined by the protocol Exclusion Criteria * Known severe allergic reactions to TCZ or other monoclonal antibodies * Active tuberculosis (TB) infection * Suspected active bacterial, fungal, viral, or other infection (besides SARS-CoV-2) * Participants who are on a mechanical ventilator \> 24 hours or extracorporeal membrane oxygenation (ECMO), in shock, or combination thereof with other organ failure requiring treatment in an ICU * In the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments * Receipt of oral anti-rejection or immunomodulatory drugs (including TCZ) within the past 3 months * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 10 x ULN detected within 24 hours at screening or at baseline (according to local laboratory reference ranges) * Absolute neutrophil count (ANC) \< 1000/uL at screening and baseline (according to local laboratory reference ranges) * Platelet count \< 50,000/uL at screening and baseline (according to local laboratory reference ranges) * Pregnancy or breastfeeding, or positive pregnancy test at a predose examination * Treatment with an investigational drug within 5 drug-elimination half-lives or 30 days (whichever is longer) of randomization