Another study aimed to elucidate genetic alterations underlying interindividual clinical variability [52]; an association was found between the homozygosity for the C allele (CC vs. CT/TT), due to the single-nucleotide polymorphism rs12252, in the interferon-induced transmembrane protein 3 (IFITM3) gene and COVID-19 severity [52]. The gene discussed is IFITM3; the disease is COVID-19.