Low Vitamin C and enhanced oxidative stress have been indicated in patients with pneumonia and sepsis. It has been reported that the administration of vitamin C to patients with pneumonia can reduce the severity and duration of the disease.

 Vitamin C possesses pleiotropic physiological functions, several of which are relevant to COVID 19. These pleiotropic effects include its antioxidant, anti-inflammatory, anti-thrombotic, and immune-modulatory functions. Studies have also reported low vitamin C status in critically ill COVID 19 patients. Vitamin A has favorably modulated host responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), particularly in the critical stages of infection. Vitamin C has a potential role in correcting a disease-induced deficiency, reducing oxidative stress, increasing interferon production, and supporting the anti-inflammatory actions of glucocorticosteroids.

In COVID 19, vitamin C enhances cortisol production and potentiates the anti-inflammatory and endothelial cytoprotective effects of glucocorticoids. While exogenous glucocorticoid steroids are the only proven treatment for COVID 19, vitamin C, being a pleiotropic stress hormone, plays a critical role in mediating the adrenocorticoid stress response, especially in sepsis. It also protects the endothelium from oxidant injury. Vitamin C downregulates the cytokine storm, protects the endothelium from oxidant injury, has an essential role in tissue repair, and improves immune responses against infections. 

Resources: 1. Carr AC, Rowe S. Nutrients. 2020; 12: 3286. 

2. Dwivedi R. News Medical Lie Sciences. Oct 23, 2020. Accessed from https://www.news-medical.net/news/20201023/Vitamin-C-and-COVID-19-A-Review.aspx