Hospitalized children with influenza A before, during and after COVID-19 pandemic: a retrospective cohort study

Abstract Context Since the outbreak of COVID-19 in late 2019, the transmission dynamics and clinical presentation patterns of influenza A (Flu A) virus have undergone changes. Objectives This article conducted a comparative analysis in clinical characteristics and laboratory results of pediatric patients with Flu A before, during, and after the COVID-19 pandemic. Methods The medical records of 885 children hospitalized with Flu A virus infection at a tertiary hospital in Guangdong Province, China, were retrospectively analyzed. Flu A was confirmed in these cases using a direct immunofluorescence antigen assay. The clinical data for this study span from January 1, 2018, to May 31, 2023. Results In our study, we observed a total of 340 cases before the COVID-19 pandemic, 196 cases during the pandemic, and 349 cases after the pandemic. Patients after the pandemic had a higher median age on admission (5.66 years, range 3.41–7.70) and exhibited more respiratory symptoms such as cough, sore throat, and nasal stuffiness. The length of hospital stay was longer, and there was a higher percentage of patients with fever duration ≥ 5 days among Flu A patients during the pandemic. Compared to before and during the COVID-19 pandemic, Flu A patients after the pandemic showed significantly reduced white blood cell (WBC) and platelet (PLT) counts (P