Effect of High Dose Intravenous Vitamin C in Severe Pneumonia

Inclusion Criteria: * Patients who are aged 18 and above * Patients who are diagnosed with severe pneumonia * Patients who are mechanically ventilated Exclusion Criteria: * Known allergy to Vitamin C * Pregnancy * Known history of ongoing concomitant infection * Participation in another clinical trial and/or receipt of investigational drugs within 4 weeks prior to enrollment * Moribund patient with multiorgan failure to the judgement of the treating physician, who is not expected to survive 24 hours * Patient who requires home oxygen therapy or mechanical ventilation, including tracheostomy or non-invasive ventilation, except for CPAP/BIPAP for sleep-disordered breathing * Known history of previous or current diagnosis of renal stones * Known diagnosis of glucose-6-phosphate dehydrogenase (G6PD) deficiency * Known diagnosis of hemochromatosis * Known diagnosis of poorly controlled chronic pulmonary disease, including: * Chronic obstructive pulmonary disease with oxygen therapy * Chronic restrictive pulmonary disease with oxygen therapy * Bronchial asthma on Step 5 of treatment ladder as shown in Pocket Guide for Asthma Management and Prevention * Lung cancer in Stage IV of disease * Known diagnosis of heart failure on anti-failure treatment or requiring mechanical hemodynamic support (e.g. LVAD), with recent hospitalization within 3 months (90 days) from the date of current admission. * Immunocompromised state * Known diagnosis of malignancy and ongoing chemotherapy or radiotherapy as there is evidence that antioxidant supplement before and during treatment was associated with an increased hazard of recurrence * Known diagnosis of malignancy who had completed chemotherapy or radiotherapy with absolute neutrophil count ≤100 cells/mm3 * Known diagnosis of Stage 4 and above chronic kidney disease (GFR \<30 ml/min/1.73m2) and end-stage renal disease on regular dialysis (including peritoneal dialysis or hemodialysis) * Known history of renal transplantation * Absence of family members or next of kin for informed consent