Introduction: Following the COVID-19 pandemic, in 2021-2022, we experienced an acute rise in the incidence of acute cellular rejection (ACR) episodes among children 1-year post liver transplant (LT) at Texas Children’s Hospital (TCH). We sought to identify clinical risk factors associated with this surge in ACR.

Methods: Baseline characteristics at or prior to time of histologically confirmed ACR were analyzed according to pre- (2018-2020) and post-COVID (2021-2022) eras using mean (SD), median (25th,75th %), or frequency (%). Unadjusted logistic regression assessed risk factors for ACR. All statistical analyses were performed using Stata v15.1.

Results: Among the 621 transplanted patients followed at our institution, 25 and 28 children were diagnosed with ACR in 2021 and 2022, respectively, representing a 2.2 and 2.5-fold increase compared to the 3 preceding years (n=11 per year, 2018-2020). Diagnosis, sex, ethnicity, and body mass index z-score were similar between eras. Post-COVID, there was a 50% increase in ACR among adolescents with a higher trend in severe ACR (RAI >6), but no differences in median MLVI. WBC, ALC and ANC were no different. Viral infections were less common (p=0.045), but not associated with increased ACR in the post-COVID era. COVID vaccination status in the higher ACR cohort mirrored the same proportion of the total transplant cohort (34%), suggesting that COVID vaccination status plays little or no role in the increased incidence of ACR.  

Conclusion: Increased ACR rates at a large tertiary pediatric transplant center was not associated with viral infections, COVID vaccination, or increased MLVI.