CD4 and chronic kidney disease: The proportion of interferon gamma (IFNƴ) producing spike-specific CD4+ T-cells of all memory CD4+ T-cells increased from 0.017 (IQR 0–0.058)% to 0.103 (IQR 0.078–0.196)% in CKD patients(p < 0.001) and 0.044 (IQR 0.036–0.124)% to 0.199 (IQR 0.112–0.280)% in controls (p < 0.05) between the first and second dose.