Predictive factors of response to 3^rd dose of COVID-19 mRNA vaccine in kidney transplant recipients

Only a minority of kidney transplant recipients (KTRs) develop protective neutralizing titers of anti-receptor binding domain of spike protein (RBD) IgG after two doses of mRNA COVID-19 vaccine. Administration of a third dose of mRNA vaccine to KTRs with sub-optimal response increase anti-RBD IgG titers but with high inter-individual variability. Patients with the higher response rate to the third dose of vaccine can be identified by the presence of low anti-RBD IgG titers and spike-specific CD4+ T cells in their circulation 14 days after the second dose.