*Purpose: Infections remain a major threat to successful kidney transplantation (KT), although there is limited data on the spectrum and clinical consequences of a post-KT infection in the current immunosuppression era.

*Methods: To characterize the landscape and impact of post-KT infections in the modern immunosuppression era, we used national data from the United States Renal Data System to study 141,664 Medicare-primary KT recipients from 1/1/1999-12/31/2014, with linkage to SRTR for accurate outcome ascertainment. Infection diagnoses were ascertained by ICD-9 codes. We used adjusted Cox regression, treating the development of a post-KT infection as a time-varying exposure, to quantify the impact of a post-KT infection on mortality and death-censored graft failure (DCGF).

*Results: The cumulative incidence of a post-KT infection was 30.3% at 3 months, 46.5% at 1 year, and 73.9% at 5 years. The most common infections were UTI (37.6%) and pneumonia (21.9%), whereas the least common were meningitis (1.6%) and zoonotic (0.2%) (Figure 1). 5-year mortality for KT recipients who developed an infection was 25.7% vs. 8.9% for those who did not, and 5-year DCGF was 22.4% vs. 10.6% (p<0.001) (Figure 2). This translated to a 2.06-fold higher mortality risk (adjusted hazard ratio [aHR]: _2.002.06_2.13, p<0.001) and 1.82-fold higher DCGF risk (aHR: _1.761.82_1.89, p<0.001) for KT recipients who developed an infection, although the magnitude of this higher risk varied across infection types (for example, 2.65-fold higher mortality risk for Clostridium difficile versus 1.37-fold for a UTI) (Figure 3).

*Conclusions: Post-KT infections are common and substantially impact mortality and DCGF, even in the modern era. Immunosuppression choices should be carefully tailored accordingly, especially in those at higher risk of infection.

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