CD4 and COVID-19: Transferring CD4+ T cell populations to T helper cell 2 (Th2) phenotypes during pregnancy (a response that promotes humoral rather than cellular immune responses) (Piccinni et al., 2000), reduced T helper cell 1 (Th1) reactivity may lead to reduced clearance of infected cells, increasing susceptibility to COVID-19 (Veenstra Van Nieuwenhoven et al., 2003).