CD4 and type 2 diabetes mellitus: However, a larger study of T2D individuals highlights that 21 days after the first vaccine dose, neutralizing antibody titers and CD4 cytokine responses involving type 1 helper T cells were lower in T2D patients with HbA1c levels greater than 7% than in individuals with HbA1c levels less than or equal to 7%, evaluated at baseline before the first vaccine dose (13).