HLA-C and COVID-19: Based on our findings, we further developed a risk prediction model for detecting severe COVID-19 cases admitted to the ICU, as well as for the identification of hospitalized vs. non-hospitalized COVID-19 cases by merging risk prediction models of unconditional ordinal logistic regressions of severity characteristics against demographic (i.e., age, sex, and sex and age interaction) and HLA-C*04:01 predictors (see Material and Methods).