Enhanced SARS-CoV-2 Antibody Response After a Third Heterologous Vector Vaccine Ad26COVS1 Dose in mRNA Vaccine-Primed Kidney Transplant Recipients

Alternative strategies to increase the immunogenicity of COVID-19 vaccines in kidney transplant recipients not responding to two or three doses of an mRNA vaccine (RECOVAC): a randomised clinical trial

“… 18 , 19 After exclusion of patients who were seropositive at time of vaccination, the response rate after repeated vaccination in our control group was only slightly higher than described in the literature. In addition, the longer time interval between the repeated and preceding vaccination in our patients (median 196 days) as compared with that in other studies (median 80–109 days) 16 , 17 might also have contributed to a relatively high seroconversion rate. 20 In any case, the fact that multiple studies have reported a considerable increase in seroresponse rate after each additional booster vaccination 21 underscores the importance of a high uptake in new booster vaccination campaigns for all KTRs.…”

“…These figures are higher than the seroconversion rates of 39 to 54% reported in other studies assessing the response to third vaccination in seronegative KTR. 16 , 17 This discrepancy might in part be related to the fact that 24% of all participants who were seronegative during screening, appeared to be seropositive at the time of repeated vaccination, which took place at a median interval of about 6 months after the preceding vaccination. Seroconversion due to COVID-19 was excluded as well as possible on the basis of the reporting of patients and the measurement of SARS-CoV-2 nucleocapsid-specific antibodies, but asymptomatic cases could have gone unnoticed since a regular screening with PCR tests was not done.…”

SARS-CoV-2 antibody responses post-vaccination in UK healthcare workers with pre-existing medical conditions: a cohort study

“…Booster mRNA vaccine doses should be prioritised for this population, in particular those with two prior ChAdOx1 doses, as evidence has shown that a third or fourth dose could significantly improve the suboptimal immune response in organ transplant recipients. [27][28][29] Other comorbidities independently associated with lower antibody levels post-vaccination were diabetes and respiratory diseases other than asthma. Antibody response and seropositivity rates in patients with diabetes were also found to be lower than in the healthy population after vaccination in a recent systematic review.…”

“…Therefore, it may be helpful to routinely assess post-vaccination antibody levels in HCWs with comorbidities, especially immunosuppression or organ transplantation. Booster mRNA vaccine doses should be prioritised for this population, in particular those with two prior ChAdOx1 doses, as evidence has shown that a third or fourth dose could significantly improve the suboptimal immune response in organ transplant recipients 27–29…”

Comparison of the Immune Response After an Extended Primary Series of COVID-19 Vaccination in Kidney Transplant Recipients Receiving Standard Versus Mycophenolic Acid–sparing Immunosuppressive Regimen

“…13,15,30,31 The heterologous COVID-19 vaccination with vector-based and mRNA vaccines improved the immune response in transplant recipients. 32,33 The priming with vector-based vaccine prior to mRNA vaccination might result in higher SARS-CoV-2-specific CD4 and CD8 T-cell levels in healthy individual compared to mRNA vaccination alone. 32 However, the distinction of these cellular immunity activation between vector-based and mRNA vaccines could not be demonstrated in the organ transplant patients.…”