*Purpose: Kidney transplant recipients are vulnerable to develop severe form of COVID19 Infection. Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine has significantly improved incidence of COVID19, seroconversion rates in immunosuppressed patients post vaccine is variable and unpredictable.

We aim to evaluate the rates of antibody response to SARS-CoV-2 mRNA vaccine and identify factors affecting immunogenicity among kidney transplant recipients

*Methods: We retrospectively reviewed 327 kidney transplant recipients who received 2 doses of mRNA Vaccine and did not develop COVID19 prior to antibody testing. SARS- CoV- 2 antibody response and risk factors associated with negative serology were evaluated after 2 doses of mRNA vaccine. Patients who tested positive were divided into four quartiles based on titers and analyzed using ANOVA.

*Results: 250 (76.5%) recipients had positive titers and 77 (24%) did not. Poor response was associated with older age (p=0.06) and male gender(p=0.03). Race, immunosuppression regimen and trough levels were not significant. Analysis of recipients who developed antibody revealed age, time from transplant, history of diabetes and steroid as factors affecting titer level (Table 1).

*Conclusions: Understanding immunologic response to SARS-CoV-2 vaccine in kidney transplant recipient is important to prevent life threatening infection. Identification of transplant recipients at risk of low vaccine response can be a guide to formulate personalized therapy

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