Vitamin C and D supplementation and the severity of COVID-19: A protocol for systematic review and meta-analysis.

Background: The COVID-19 pandemic has rapidly spread to other countries, causing numerous deaths and challenges for organizations and health professionals. Diet and nutrition invariably influence the competence of the immune system and determine the risk and severity of infections. Studies have already been published on the relationships through which vitamins C and D can mitigate the severity of infections such as COVID-19.