Risk Factors for Coronavirus Disease 2019 Hospitalization and Vaccination Impact Among Pediatric Solid Organ Transplant Recipients in the United States

BACKGROUND: While vaccination is a key strategy to mitigate the severity of coronavirus disease 2019 (COVID-19) in children, the risk factors for symptomatic, medically attended (hereon referred to as "symptomatic") COVID-19 and the impact of vaccination are not well defined among pediatric solid organ transplant recipients (PSOTR). METHODS: PSOTR aged six months through 21 years at 11 centers in the Pediatric Infectious Diseases Transplant Network (PIDTRAN) were analyzed retrospectively for symptomatic COVID-19 between July 2021 and May 2023. Using a Cox proportional hazards model, risk factors associated with COVID-19-associated hospitalization, in-hospital oxygen use, mechanical ventilation, and the impact of COVID-19 vaccination were analyzed. RESULTS: Of 1370 PSOTR, 410 (29%) had symptomatic COVID-19 infection. Among those with symptomatic infection, 115 (28%) were hospitalized, 35 required in-hospital oxygen, and three required mechanical ventilation. In the study, 45% were unvaccinated against COVID-19. Compared to unvaccinated PSOTR, incompletely vaccinated PSOTR had 56% lower hazard (95% CI 0.26, 0.72, p = 0.001) of COVID-19-associated hospitalization whereas completely vaccinated did not have a statistically significant difference in hazard of hospitalization. Receipt of at least one dose of the bivalent vaccine was also associated with 92.5% lower hazard (95% CI 0.010, 0.55, p = 0.011) of hospitalization. Risk factors for hospitalization included chronic kidney disease, underlying heart disease, neurodevelopmental delay, and lymphocytopenia. CONCLUSIONS: Most PSOTR with symptomatic COVID-19 did not require hospitalization or respiratory support. Several comorbidities and lymphocytopenia are associated with severe COVID-19 in PSOTR. COVID-19 vaccination, mostly, protected PSOTR against COVID-19-associated hospitalization, but vaccine uptake among PSOTR was low.