Differences in the clinical course of COVID-19 in children and adolescents hospitalized in the 2023/2024 and 2024/2025 seasons - a retrospective real-world study.

BACKGROUND: This multicenter retrospective study was designed to track changes in the clinical presentation of COVID-19 in children that occurred in the last two infectious seasons, and to identify risk factors for severe disease progression. METHODS: The analysis covered all consecutive children hospitalized due to COVID-19 during the 2023/2024 and 2024/2025 infectious seasons in Polish pediatric centers. RESULTS: Of the 366 children included in the study, 203 were hospitalized in the first period analyzed and 163 in the second. In both seasons, about three-quarters of the population were children under 2 years of age, boys were hospitalized more often than girls and more than a one-fourth had comorbidities. Oxygen saturation (SpO2) upon admission was significantly lower in the 2023/2024 season. Children in unstable clinical condition with SpO2 ≤ 95% were admitted to hospital statistically more often in the first period analyzed. Eleven patients were admitted in unstable clinical condition with SpO2 < 90%, nine of whom were hospitalized during the period 2023/2024. Nine of them were aged one year or younger, and seven had comorbidities. Oxygen supplementation was used significantly more often in the first period analyzed, high-flow therapy was used in three children hospitalized in the 2023/2024 season, while one child required mechanical ventilation in the 2024/2025 season. CONCLUSIONS: With each season of Omicron dominance, the course of COVID-19 in pediatric patients is becoming milder. Special attention should be paid to the youngest children and those with comorbidities, as the disease may progress more rapidly and lead to severe course in this population. CLINICAL TRIAL NUMBER: Not applicable.