Immunogenicity After a Heterologous BNT262b2 Versus Homologous Booster in Kidney Transplant Recipients Receiving 2 Doses of CoronaVac Vaccine: A Prospective Cohort Study.

BACKGROUND: Comparative studies of third heterologous doses following the CoronaVac vaccine against coronavirus disease 2019 (COVID-19) in kidney transplant recipients are lacking. METHODS: This prospective, single-center cohort study included kidney transplant recipients without previous COVID-19. Patients received a third heterologous (BNT162b2 mRNA) or homologous dose at least 4 wk after 2 doses of the CoronaVac vaccine. Immunoglobulin G antibody response and seroprevalence for neutralizing anti-severe acute respiratory syndrome coronavirus 2 antibodies immediately before and 28 d after third doses were compared between the groups. RESULTS: There were 307 patients in the heterologous group and 777 in the homologous group. Patients in the heterologous group were older (54 versus 50 y; P < 0.0001), with a longer time since transplant (11 versus 6 y; P < 0.0001). Immediately before the third dose, immunoglobulin G seroprevalence (36% versus 34%; P = 0.597) and antibody titers (246 versus 268 AU/mL; P = 0.279) were similar. After booster, seroconversion was higher in the heterologous group (49% versus 32%; P < 0.0001), resulting in a higher seroprevalence (67% versus 55%; P = 0.0003); however, 42% of all patients remained seronegative. Antibody titers after booster in seropositive patients were higher in the heterologous group (7771 versus 599 AU/mL; P < 0.0001). These results persisted after adjusting for confounding variables. Lastly, a similar proportion of patients became seropositive for neutralizing antibodies (98% versus 94%; P = 0.098). CONCLUSIONS: In kidney transplant recipients fully vaccinated with CoronaVac, a third dose with an mRNA vaccine produced a higher seroconversion rate and antibody titers than a third homologous dose. However, both boosters achieved equivalent seroprevalence for neutralizing antibodies. The high proportion of still seronegative patients indicates the need for alternative strategies of protection.

Targeted preemptive therapy according to perceived risk of CMV infection after kidney transplantation.

BACKGROUND: The identification of the best strategy to manage cytomegalovirus infection is hampered by uncertainties regarding the risk/benefit ratios of universal prophylaxis versus preemptive therapy, the impact of indirect cytomegalovirus effects and the associated costs. This study investigated the efficacy and safety of targeted preemptive therapy according to perceived risk of cytomegalovirus infection after kidney transplantation. METHODS: 144 adult kidney transplant recipients were enrolled in this 12-month study. None received cytomegalovirus pharmacological prophylaxis. Only high risk patients (positive donor/negative recipient (D+/R-), use of induction therapy with antithymocyte globulin, treatment of rejection) received preemptive therapy based on the result of pp65 antigenemia test. Low-risk patients with symptoms related to cytomegalovirus were screened for pp65 antigenemia and treatment initiated if confirmed cytomegalovirus disease. Blinded cytomegalovirus DNAemia was collected weekly during the first three months. RESULTS: The incidence of cytomegalovirus infection was 34% and cytomegalovirus disease was 17%. The incidence was 25% in D+/R-, 69% in those receiving induction with rabbit antithymocite globulin (r-ATG), 46% in those treated for acute rejection, and 28% in low risk patients. By week 3 DNAemia was observed in 30% of patients who were not treated for cytomegalovirus infection/disease, and values ≥2.169UI/mL showed 61% sensitivity and 85% specificity to detect cytomegalovirus disease (AUC=0.849±0.042, p<0.001). Using multivariate analysis, only anti-thymocyte globulin induction was associated with cytomegalovirus infection/disease whereas only expanded donor criteria and renal function at 30 days were associated with renal function 12 months after transplantation. CONCLUSION: Targeted preemptive therapy in patients with perceived higher risk for cytomegalovirus infection/disease was effective in preventing severe clinical presentation, including tissue invasive and late cytomegalovirus infection. This strategy is associated with direct and indirect cost-savings.