Trial Evaluating Efficacy and Safety of Nivolumab (Optivo®) in Patients With COVID-19 Infection, Nested in the Corimmuno-19 Cohort.

Inclusion Criteria: * Adults (men and women) age over 18 years old * At least one nasal swab positive for COVID-19 detected by PCR, maximum 7 days prior to treatment * Viral pneumonia confirmed by TDM scan * Patients meeting all of the following 3 criteria: * Requiring more than 3L/min of oxygen * WHO progression scale = 5 * No NIV or High flow Exclusion Criteria: * Patients with active cancer and immunocopromised patients * Known hypersensitivity to nivolumab or to any of their excipients. * Pregnancy * Patient with an autoimmune or inflammatory disease (including but not limited to: Crohn's Disease, rheumatoid arthritis, scleroderma, systemic lupus erythematosus, Grave's disease). Patients with thyroiditis or vitiligo only could be included. * Patient with a history of thymoma * Patient with a history of solid organ transplantation or a bone marrow transplantation * Patients treated with immune checkpoint inhibitors 3 months prior to the study * Patients who had a history of grade 3 or 4 immune-related adverse events with a previous treatment with immune-checkpoint inhibtors * Patients requiring ICU based on Criteria of severity of COVID pneumopathy * Respiratory failure requiring mechanical ventilation or extracorporeal membrane oxygenation