Risk Factors of COVID-19 Severity and Related Death in Children in the Post-Pandemic Era.

In the post-pandemic era, identifying children who are most susceptible to severe illness and COVID-19-related mortality is essential for guiding public health policies. This study examined the risk factors for COVID-19-related severe illness and mortality from 2023 to mid-2025. We conducted a population-based cohort study using nationwide Brazilian data from patients aged <18 years with laboratory-confirmed SARS-CoV-2 infection between January 2023 and June 2025. The primary outcomes were COVID-19-related severity and death. Separate binary multivariable logistic regression models were developed for each of the outcomes. Among 465,689 children, 1.3% (n = 5963) developed severe illness, and 0.18% (n = 847) died. Factors associated with an increased risk of severe illness included age < 2 years, presence of comorbidities, Indigenous ethnicity, and lack of vaccination. Neurological disorders conferred the highest risk among the clinical conditions (adjusted odds ratio [aOR] = 34.1; 95% CI: 27.9-41.8). Regional differences were also observed; the North and Northeast regions showed higher mortality (aOR = 2.3; 95% CI: 1.8-3.0) than the Central-West region. Compared with White ethnicity, non-White ethnicities had higher mortality: Indigenous (aOR = 23.5; 95% CI: 13.5-39.3), Black (aOR = 1.95; 95% CI: 1.29-2.92), and Brown (aOR = 1.43; 95% CI: 1.18-1.73) ethnicities. Lack of any vaccine dose was associated with a significantly increased risk of severe illness (aOR = 1.39; 95% CI: 1.15-1.67. p < 0.001) and death (aOR = 2.1; 95% CI: 1.3-3.5; p < 0.001). In the post-pandemic era, younger age, comorbidities, sociodemographic disparities, and lack of vaccination were associated with an increased risk of severe illness and COVID-19-related death in the pediatric population.