Community-Acquired Pneumonia : Evaluation of Corticosteroids

Inclusion Criteria: * Age ≥ 18 years * Patients affiliated to social security scheme * Admission to an Intensive Care Unit (ICU) or intermediate care unit participating to the trial * Diagnosis of Community- Acquired Pneumonia (CAP) suggested by at least two of the following: cough, purulent sputum, chest pain and dyspnea * Focal shadowing/infiltrate on chest X-ray or CT-scan * Diagnosis of Community- Acquired Pneumonia (CAP) during the 48 hours post-hospital admission * Study drug infusion initiated no longer than 24 hours post first severity criterion * Severity defined by at least one of the following: * Pneumonia Severity Index (PSI) \> 130 (Fine class V) * Patient placed on mechanical ventilation (invasive or not) for acute respiratory failure, with a PEEP level of 5 cm of water or more * Patient treated by high-flow oxygen therapy with a FiO2 of 50% or more and a P/F ratio less than 300 * Patient treated by oxygen therapy with a partial rebreathing-mask with a reservoir bag, provided that the PaO2 is less than (cf. table): Oxygen flow (L/min) 6 7 8 9 10 or more PaO2 (mmHg) less than 180 210 240 270 300 * Patient already treated by antibiotics (at least one dose since admission to hospital) * Informed consent signed by the patient, its relatives or emergency procedure On the sub-group of patients included with COVID19 : * Diagnosis of COVID19 either as certain (PCR) or probable (evocative clinical and radiological features AND epidemic context AND absence of other microbiological documentation). * Study drug infusion initiated no longer than 24 hours post first severity criterion ; in case of transfer from another hospital, this period will be prolonged to 48 hours * Patient receiving the best available treatment as define by up-to-date scientific knowledge Exclusion Criteria: * Patient treated by vasopressors for septic shock at the time of inclusion * Clinical history suggesting of aspiration of gastric content * Patient treated by invasive mechanical ventilation within 14 days before current hospital admission * Patient treated by antibiotics for a respiratory infection for more than seven days at the admission to the hospital (except if a pathogen resistant to this antibiotics is isolated) * History of cystic fibrosis * Post-obstructive pneumonia * Patients in which rapid PCR-test is positive for flu * Active tuberculosis or fungal infection * Active viral hepatitis or active infection with herpes viruses * Myelosuppression * Decision of withholding mechanical ventilation or endotracheal intubation * Hypersensitivity to corticosteroids * Patient needing anti-inflammatory corticosteroids or substitutive hydrocortisone for any reason * Patients under treatment by more than 15 mg/d of prednisone (or equivalent) for more than 30 days * Patient already enrolled in another drug trial with mortality as an end-point. If the patient is already participating in another therapeutic trial with a different endpoint, the investigator must verify that inclusion in CAPE COD can not prejudice it. * Pregnant or breastfeeding woman * Patient on judicial protection