SARS-CoV-2-specific Humoral and Cell-mediated Immune Responses after Immunization with Inactivated COVID-19 Vaccine in Kidney Transplant Recipients (CVIM 1 Study).

Immunogenicity following inactivated SARS-CoV-2 vaccination among solid organ transplant recipients has not been assessed. Seventy-five patients (37 kidney transplant [KT] recipients and 38 healthy controls) received two doses, at 4-week intervals, of an inactivated whole-virus SARS-CoV-2 vaccine. SARS-CoV-2-specific humoral (HMI) and cell-mediated immunity (CMI) were measured before, 4 weeks post-first dose, and 2 weeks post-second dose. The median (IQR) age of KT recipients was 50 (42-54) years and 89% were receiving calcineurin inhibitors/mycophenolate/corticosteroid regimens. The median (IQR) time since transplant was 4.5 (2-9.5) years. Among 35 KT patients, the median (IQR) of anti-RBD IgG level measured by CMIA after vaccination was not different from baseline, but was significantly lower than in controls (2.4[1.1-3.7] vs. 1,742.0 [747.7-3,783.0] AU/mL, p<0.01) as well as percentages of neutralizing antibody inhibition measured by surrogate viral neutralization test (0[0-0] vs. 71.2[56.8-92.2]%, p<0.01). However, the median (IQR) of SARS-CoV-2 mixed peptides-specific T-cell responses measured by ELISpot was significantly increased compared with baseline (30[4-120] vs. 12[0-56] T-cells/106 PBMCs, p=0.02) and not different to the controls. Our findings revealed weak HMI but comparable CMI responses in fully vaccinated KT recipients receiving inactivated SARS-CoV-2 vaccination compared to immunocompetent individuals. (Thai Clinical Trials Registry,TCTR20210226002).