In their observational study including 30 pregnant, 16 lactating, and 57 non-pregnant individuals, Collier and colleagues also assessed cellular immune responses to the mRNA COVID-19 vaccines, quantifying the percent of spike-specific IFN-γ production by CD4 T cells, CD4 central memory T cells, CD8 T cells, and CD8 central memory T cells. This evidence concerns the gene CD4 and COVID-19.