Comparison of humoral and cellular responses in kidney transplant recipients receiving BNT162b2 and ChAdOx1 SARS-CoV-2 vaccines

Background Attenuated immune responses to mRNA SARS-CoV-2 vaccines have been reported in solid organ transplant recipients. Most studies have assessed serological responses alone, and there is limited immunological data on vector-based vaccines in this population. This study compares the immunogenicity of BNT162b2 with ChAdOx1 in kidney transplant patients, assessing both serological and cellular responses. Methods 920 patients were screened for spike protein antibodies (anti-S) following 2 doses of either BNT162b2 (n=490) or ChAdOx1 (n=430). 106 patients underwent assessment with T-cell ELISpot assays. 65 health care workers were used as a control group. Results Anti-S was detected in 569 (61.8%) patients. Seroconversion rates in infection-naïve patients who received BNT162b2 were higher compared with ChAdOx1, at 269/410 (65.6%) and 156/358 (43.6%) respectively, p<0.0001. Anti-S concentrations were higher following BNT162b, 58(7.1-722) BAU/ml, compared with ChAdOx1, 7.1(7.1-39) BAU/ml, p<0.0001. Calcineurin inhibitor monotherapy, vaccination occurring >1st year post-transplant and receiving BNT162b2 was associated with seroconversion. Only 28/106 (26.4%) of patients had detectable T-cell responses. There was no difference in detection between infection-naïve patients who received BNT162b2, 7/40 (17.5%), versus ChAdOx1, 2/39 (5.1%), p=0.15. There was also no difference in patients with prior infection who received BNT162b2, 8/11 (72.7%), compared with ChAdOx1, 11/16 (68.8%), p=0.83. Conclusions. Enhanced humoral responses were seen with BNT162b2 compared with ChAdOx1 in kidney transplant patients. T-cell responses to both vaccines were markedly attenuated. Clinical efficacy data is still required but immunogenicity data suggests weakened responses to both vaccines in transplant patients, with ChAdOx1 less immunogenic compared with BNT162b2.