Patient Inclusion Criteria

- Documented COVID19 pneumonia (positive SARS-CoV2 test, bilateral abnormalities/ infiltrates on chest x-ray or computed tomography, active fever or documented fever within 24-48 or ongoing anti-pyretic use to suppress fever). - Hypoxia (room air SpO2 <92% or requirement for supplemental oxygen). - Increased serum inflammatory markers (CRP > 5 mg/dl AND LDH >upper limit of normal for local laboratory).

Patient Exclusion Criteria

- Onset of COVID-19 >14 days - Hospitalized >7 days - Mechanically ventilated - Age <18 years-old - Neutropenia (absolute neutrophil count <1,500/mm3) - Serious concomitant illness which in the opinion of the investigator precludes the patient from enrolling in the trial, including (but not limited to): - History of immunodeficiency (congenital or acquired) - History of solid-organ or bone marrow transplant - History of current systemic autoimmune or autoinflammatory disease(s) requiring systemic immune-modulating drugs - History of myeloproliferative disorder or active malignancy receiving cytotoxic chemotherapy - Pre-existing severe pulmonary disease (i.e. asthma, COPD, or others) - Pre-existing severe left ventricular systolic dysfunction (i.e. LVEF <35%) - Known active tuberculosis (TB) or history of incompletely treated TB or at high risk for latent TB (for exposure or prior incarceration) - Concomitant systemic bacterial or fungal infection - Concomitant viral infection other than COVD-19 (e.g. influenza) - History of chronic liver disease with portal hypertension - History of end-stage renal disease on chronic renal replacement therapy - Recent treatment with cell-depleting biological therapies (e.g., anti-CD20) within 12 months noncell-depleting biological therapies (such as anti-tumor necrosis factor-alpha [TNF-alpha], anakinra, anti-Interleukin [IL]-6 receptor [e.g. tocilizumab], or abatacept) within 8 weeks (or 5 half-lives, whichever is longer), treatment with alkylating agents within 12 weeks, treatment with cyclosporine A, azathioprine, cyclophosphamide, or mycophenolate mofetil (MMF) within 4 weeks - Recent treatment with intramuscular live (attenuated) vaccine within the 4 weeks - Chronic or recent corticosteroid use - Pregnancy or lactation or newborn - Enrolled in another investigational study using immunosuppressive therapy - Enrolled in a blinded clinical trial of any type - Known hypersensitivity to Mavrilimumab or any of its excipients - In the opinion of the investigator, unable to comply with the requirements to participate in the study