5,10 methylenetetrahydrofolate reductase (FADH2) 1 Alleles 1 Article 1 C677T gene 1 C677 T mutation prevalence 1 COVID-19 1 COVID-19 vulnerability Ethnic Groups 1 Gene Frequency 1 Genetic Predisposition to Disease 1 Hispanic 1 Homocysteine 1 Humans 1 MTHFR gene 1 Methylenetetrahydrofolate Reductase (NADPH2) 1 Prevalence 1 allele 1 coronavirus disease 2019 1 correlational study 1 disease predisposition 1 disease severity 1 disease transmission 1 enzymology 1 epidemiology 1 ethnic group 1 gene 1 gene frequency 1 gene mutation 1 genetic correlation 1 genetic polymorphism 1