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

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

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

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