Changes in epidemiological and clinical features in children before, during, and after the COVID-19 pandemic in Shanghai, China.

Non-pharmaceutical interventions (NPIs) implemented during the COVID-19 pandemic had a significant impact on the epidemiology of respiratory pathogens. Following the relaxation of these measures, a notable increase in (Mp) pneumonia incidence among children was observed. To comprehensively analyze the impact of NPIs on the patterns of Mp infections in children, we assessed changes in the epidemiology and clinical features of Mp infections in Songjiang District, Shanghai, before, during, and after the pandemic. A total of 6,050 hospitalized children with community-acquired pneumonia (CAP) from January 2017 to December 2024 were included. Annual Mp epidemiology was analyzed from 2017 to 2024. To assess NPI-specific effects, three comparative phases were defined: Before (June 2017-May 2019, pre-pandemic), During (June 2020-May 2022, active pandemic with NPIs), and After (June 2022-May 2024, post-NPIs). Epidemiological characteristics, clinical features, and laboratory findings were systematically compared across these phases. From 2017 to 2024, the number of hospitalized CAP cases significantly decreased from 2020 to 2022, with an overall Mp positivity rate of 43.16%. Annual Mp positivity rate peaked at 56.32% in 2022 versus 30.70% in 2020. Intergroup comparisons revealed that the After group exhibited the highest Mp positivity rate (56.03%), significantly exceeding both the Before (28.59%) and During (41.63%) groups. Notably, the After group exhibited significantly lower white blood cell count (WBC) and C-reactive protein (CRP), alongside elevated platelet count (PLT) and alanine aminotransferase (ALT). The proportion of patients with low Mp antibody titers (1:80) was significantly higher in the During group, whereas high-titer categories (1:320 and >1:640) predominated in the After group. NPIs during the COVID-19 pandemic significantly altered the epidemiology and clinical features of Mp infections in children in Songjiang District, Shanghai.IMPORTANCEThis study examines the effects of non-pharmaceutical interventions (NPIs) during the COVID-19 pandemic on the epidemiology of (Mp) infections in children. By analyzing data from over 6,000 hospitalized children with community-acquired pneumonia, the research reveals a significant change in Mp infection patterns, with a marked increase in positivity rates after NPIs were relaxed. The findings indicate a shift in the affected demographic, with more school-age children presenting with Mp infections, as well as variations in clinical features such as different laboratory results. This research provides valuable insights for healthcare professionals in understanding the implications of NPIs on respiratory infections in children, guiding future treatment approaches and public health strategies. It represents a meaningful contribution to the ongoing evaluation of pediatric health in a post-pandemic context.