Fig 3. Correlation between pre-infection vitamin D deficiency status and COVID-19 disease severity stratified by three different groups of age (<50, 50–64, ≥65).

The severity of illness (critical, severe, moderate, and mild, as determined by the WHO definition of COVID-19 disease severity (WHO/2019-nCoV/clinical/2020.5)). The regression fit for each age group is shown. Values that are more than two SD away from the regression fit to the rest of the data were omitted from the analysis (applicable for two values appear on <50 yr graph that omitted from regression fit calculation).