Univariate regression analysis demonstrated that being >80 years old, being unvaccinated/partially vaccinated, and having increased WBCs and D-dimer levels, decreased lymphocyte counts and levels of CD3+ T cells, CD4+ T cells, CD8+ T cells, B cells, and NK cells, chronic kidney disease, and cerebrovascular disease were risk factors for COVID-19 progression. This evidence concerns the gene CD8A and COVID-19.