Carriers of these common genetic variations in CYP2C19 *2 and *3 alleles, which lead to a loss of functional protein and decreased clopidogrel active metabolite levels, have significantly high platelet reactivity on-treatment and a resultant increased risk of recurrent stroke and composite vascular events when treated with clopidogrel (Pan et al., 2017; Pereira et al., 2019; Xu et al., 2019). Here, CYP2C19 is linked to Stroke.