However, there was a significant negative correlation between anti-SARS-CoV-2 antibody level and CD4/CD8 ratio (Spearman’s correlation coefficient −0.4, p = 0.02), and the relative number of CD8+ T cells (r = 0.41, p = 0.01) in responders to the COVID-19 vaccine. The gene discussed is CD8A; the disease is COVID-19.