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 non-transplant 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 age of KT recipients was 50 years (IQR, 42-54) and 89% were receiving calcineurin inhibitors/mycophenolate/corticosteroid regimens. The median time since transplant was 4.5 years (IQR, 2-9.5). Among 35 KT patients, anti-RBD IgG titer after vaccination was not significantly different to baseline, but was significantly lower than in controls (7.8 [95%CI 0.2-15.5] vs 2,691 [95%CI 1,581-3,802], p<0.001) as well as the percentage of surrogate virus neutralizing antibody inhibition (2 [95% CI -1-6] vs 71 [95%CI 61-81], p<0.001). However, the mean of SARS-CoV-2 mixed peptides-specific T-cell responses measured by enzyme-linked immunospot assays was significantly increased compared with baseline (66 [95%CI 36-99] vs. 34 [95%CI 19-50] T-cells/106 PBMCs, p=0.02) and comparable to that in controls. Our findings revealed weak HMI and marginal CMI responses in fully vaccinated KT recipients receiving inactivated SARS-CoV-2 vaccine. (Thai Clinical Trials Registry, TCTR20210226002).