*Purpose: The purpose of this study was to study our cohort of adult solid organ transplant recipients who had been infected with SARS-CoV-2 to describe the incidence density of SARS-CoV-2 re-infection, as well as the clinical features and convalescent immunity profile.

*Methods: Incidence density was calculated as the total cases of re-infection divided by total days after initial diagnosis with active graft. We included those with initial infection diagnosed by polymerase chain reaction before or after transplantation, and cycle threshold values were obtained when possible. Two recipients had immunity evaluated in the weeks prior to re-infection, by measuring IgG antibody titer to the SARS-CoV-2 receptor binding domain and virus-specific CD4+ and CD8+ T-cell reactivity following stimulation with SARS-CoV-2 peptide pools and using activation induced marker assays.

*Results: Out of 210 infected recipients, 5 (2.4%) developed re-infection, including two that had received full mRNA vaccination, but none developed hypoxia. The incidence density was 9.4 (95% confidence interval 3.9-22.6) cases/100,000 patient days. Two cases of re-infection had participated in our immunity study and had convalescent immunity data from a blood draw approximately six months after initial infection and prior to re-infection. Both mounted virus specific CD4 T cell responses prior to re-infection (1.19% and 0.28% of total CD4 T cells) and both had reactive IgG testing (1.30 and 4.99 signal/cut off ratio).

*Conclusions: This suggests that SOT recipients infected with SARS-CoV-2 remain at high risk for re-infection even after generating reactive cellular and humoral immune responses.

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