COVID-19(9) Result(7) pandemic(7) severe COVID-19(6) Vitamin(6) infections(6) Patient(6) COVID-19 patient(5) coronavirus(5) cause(5) COVID-19 pathogenesis(4) Immune homeostasis(4) retinoic acid(4) indication(4) was measured(4) severe COVID-19 patient(4) serum(4) Immunopathogenesis(4) significantly lower(4) no significant difference(4) statistically significant(4) Respiratory failure(4) Gender(4) RSV(4) vitamin A(4) Signaling(4) Depletion(4) not affect(4) SARS-CoV2(4) Type-I IFN(4)