CD8A and COVID-19: Although memory B cells and antiviral antibodies are not detectable for a long time, patients suffering from these infections display virus‐specific memory CD8+ T cells that last 6–11 years.[163] Similarly, the antibody response drops after three months in COVID‐19 patients.[164] Furthermore, certain vaccinations are ineffective against the delta version of COVID‐19, which is more contagious and easily spread than other COVID‐19 variants.