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 CLIA after vaccination was not different from baseline, but was significantly lower than in controls (2.4 [1.1–3.7] vs. 1742.0 [747.7–3783.0] AU/ml, p < .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 < .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/10 6 PBMCs, p = .02) and not different from 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).

Vaccination with inactivated SARS-CoV-2 virus produces suboptimal immune responses among kidney transplant (KT), peritoneal dialyzed (PD), and hemodialyzed (HD) patients. Participants were vaccinated with two-dose inactivated SARS-CoV-2 vaccine (V2) and a third dose of ChAdOx1 nCoV-19 vaccine (V3) at 1–2 months after V2. We enrolled 106 participants: 31 KT, 28 PD, and 31 HD patients and 16 controls. Among KT, PD, and HD groups, median (IQR) of anti-receptor binding domain antibody levels were 1.0 (0.4–26.8), 1092.5 (606.9–1927.2), and 1740.9 (1106–3762.3) BAU/mL, and percent neutralization was 0.9 (0–9.9), 98.8 (95.9–99.5), and 99.4 (98.8–99.7), respectively, at two weeks after V3. Both parameters were significantly increased from V2 across all groups (p < 0.05). Seroconversion and neutralization positivity rates in PD, HD, and control groups were 100% but were impaired in KT patients (39% and 16%, respectively). S1-specific T-cell counts were increased in PD and HD groups (p < 0.05) but not in KT patients. The positive S1-specific T-cell responder rate was > 90% in PD, HD, and control groups, which was higher than that in KT recipients (74%, p < 0.05). The heterologous inactivated virus/ChAdOx1 nCoV-19 vaccination strategy elicited greater immunogenicity among dialysis patients; however, inadequate responses remained among KT recipients (TCTR20210226002).

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