CD8A and diabetes mellitus: Vaccines address inherent immune deficits as follows: in patients with diabetes or cardiac problems with impaired CD8+ T-cell activity and excess proinflammatory cytokines (see Section 3.1), they restore CD8+ T-cell-mediated clearance and induce virus-specific IgG/IgA, limiting viral replication and immune decline and breaking the influenza–chronic disease cycle.