CD8A and autoimmune disease: Stepwise multivariate model analysis identified age, history of allergy, atopy, or asthma, autoimmune disorder complications, days since the first and second vaccinations, hemoglobin, MCV, lymphocyte count, and the percentage of naïve phenotype cells in CD8+ T cells as independent predictors of peak IgG titers (Adjusted R-squared; Full model: 0.163, selected model: 0.235) (Table 4).