IL6 and COVID-19: Post-hoc analysis revealed that the serum concentrations of anti-N IgG antibodies, IgG total, IgG4 and IL-6 were significantly higher in COVID-19 patients than in vaccinated (p < 0.001, p = 0.050, p = 0.037, p = 0.041, respectively) and non-vaccinated controls (p < 0.001, p < 0.001, p = 0.019, p < 0.005, respectively).