Heterologous high dose SARS-CoV-2 mRNA vaccine booster may improve immune response in seronegative kidney transplant recipients

Introduction: Three-dose mRNA vaccination against COVID-19 is unable to elicit a sufficient immune response in immunocompromised subjects. Methods: The aim of the study was to conduct a retrospective evaluation of the efficacy of a heterologous mRNA booster with mRNA-1273 in constantly seronegative kidney transplant recipients (KTRs) after three doses of the BNT162b2 mRNA vaccine. Twelve seronegative KTRs received a mRNA-1273 booster 5 months after the third dose of BNT162b2. Results: A total of 5 out of 12 patients (41.7%) seroconverted, with a mean titer of 353 BAU/ml. Conclusions: The administration of a heterologous mRNA vaccine as a booster may be an effective alternative for achieving post-vaccination immunity in seronegative KTRs.