Since HBsAg-specific IgG secretion after HBV vaccination is generated via B-cell activation by CD4+ Th1-helper responses [35], [36], we speculate that the reduction in CD4+ T counts and functional defects induced by gestational zinc deficiency could weaken B cells activation and proliferation, and eventually result in a decrease in HBsAg-specific IgG secretion. Here, CD4 is linked to Zinc deficiency.