CD8A and COVID-19: Another potential difference is that AIDS primarily targets CD4 T cells while COVID-19 appears to affect CD8 T cells more than CD4 T cells in mild cases of COVID-19, as evidenced by a greater reduction or cytotoxic response of CD8 T cells compared with CD4 T cells in these cases in several studies [280,281,282,283], though this trend was not supported by other studies [284,285].