Epidemiology and Clinical Characteristics of Laboratory-Confirmed COVID-19 and Influenza Infections in Children: A 2015–2024 Study in Taiwan

The COVID-19 pandemic and Taiwan's strict prevention policies from May 2020 to April 2023 significantly altered the epidemiology of viral infections. This study analyzed pediatric COVID-19 and influenza cases at Wei Gong Memorial Hospital from January 2015 to March 2024. Clinical features were compared among children hospitalized during the Omicron BA.2.3.7 (April-July 2022), Omicron BA.5 (August-December 2022), and Omicron JN.1 (2024) waves and those with influenza in 2024 and 2015-2016. Between 2015 and 2024, there were 2729 influenza A (36.6%), 974 influenza B (13.1%), and 3752 COVID-19 (50.3%) cases, with 84.7% of COVID-19 cases occurring in May-December 2022. In 2024, high fever (>40 °C) was more common in influenza A cases (32.9%) than in COVID-19 or influenza B (<i>p</i> < 0.004). Leukocytosis (>12,000/µL) was more frequent in COVID-19 cases (33.3%) than in influenza A (12.2%) or B (0%) (<i>p</i> < 0.001). Pneumonia was more prevalent in COVID-19 cases in 2024 (27.3%) than in 2022 (<i>p</i> ≤ 0.030), and pneumonia rates for influenza A (14.8%) and B (16.7%) in 2024 exceeded those in 2015-2016 (<i>p</i> ≤ 0.030). Increased pneumonia rates in 2024 emphasize the importance of vigilance and timely intervention for pediatric COVID-19 and influenza cases.