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 (p < 0.004). Leukocytosis (>12,000/µL) was more frequent in COVID-19 cases (33.3%) than in influenza A (12.2%) or B (0%) (p < 0.001). Pneumonia was more prevalent in COVID-19 cases in 2024 (27.3%) than in 2022 (p ≤ 0.030), and pneumonia rates for influenza A (14.8%) and B (16.7%) in 2024 exceeded those in 2015–2016 (p ≤ 0.030). Increased pneumonia rates in 2024 emphasize the importance of vigilance and timely intervention for pediatric COVID-19 and influenza cases.

Background: To date, no study has compared the clinical characteristics of Mycoplasma pneumoniae-associated segmental/lobar pneumonia, Mycoplasma bronchopneumonia, and COVID-19 pneumonia primarily caused by the NB.1.8.1 variant in children. Methods: We examined the epidemiologic trends of pneumonia, segmental/lobar pneumonia, and COVID-19 pneumonia at a teaching hospital from 2015 to 2025. In addition, we compared the clinical characteristics of children hospitalized with Mycoplasma segmental/lobar pneumonia, Mycoplasma bronchopneumonia, and COVID-19 pneumonia during the NB.1.8.1 variant wave in 2024–2025. Results: Between 2015 and 2024, 10,601 pneumonia cases were identified, including 525 cases of segmental/lobar pneumonia and 162 cases of COVID-19 pneumonia. An outbreak of segmental/lobar M. pneumoniae pneumonia and COVID-19 pneumonia occurred in Taiwan during 2024–2025. Starting in early 2025, monthly Mycoplasma positivity rates among children with segmental/lobar pneumonia and bronchopneumonia exceeded 60%. Mycoplasma pneumonia predominantly affected children aged 6–11 years, whereas COVID-19 pneumonia mainly occurred in those younger than 3 years of age. Fever, cough, and rhinorrhea were the most common symptoms in all groups, limiting clinical differentiation. Children with segmental/lobar Mycoplasma pneumonia were more likely to present with prolonged fever (>5 days), lymphocytopenia, a neutrophil-to-lymphocyte ratio (NLR) ≥ 3, and elevated C-reactive protein (CRP) levels, each of which was strongly associated with macrolide non-response (all p < 0.001). Conclusions: Children with segmental/lobar Mycoplasma pneumonia demonstrated more severe clinical manifestations. Segmental/lobar involvement and inflammatory markers, such as lymphocytopenia, elevated NLR, and increased CRP levels, were associated with macrolide non-response. These indicators may help guide therapeutic decision-making in pediatric M. pneumoniae pneumonia.