Epidemiological shifts and clinical characteristics of childhood Chlamydia pneumoniae pneumonia in Beijing before, during, and after public health interventions (2017–2025)

To systematically explore the impact of public health intervention measures (including strict non-pharmaceutical interventions and subsequent relaxation) on the epidemiological trends and clinical characteristics of childhood Chlamydia pneumoniae (CP) pneumonia in Beijing, and provide evidence for precise prevention, control, diagnosis, and treatment. A retrospective cohort study was conducted on 331 hospitalized children with laboratory-confirmed CPP pneumonia (January 2017–September 2025) from the Capital Center for Children’s Health. Patients were stratified into three groups based on the intensity of population-level public health non-pharmaceutical interventions(NPIs) implemented in Beijing. Demographic data and clinical characteristics were collected. Among the 331 patients (male: female ratio = 1.75:1), a significant surge was observed from January to September 2025 in the post-intervention group, which accounted for 7.91% (133 patients) of community-acquired pneumonia (CAP) cases. The primary affected age group shifted from 0 to 3 years (60.4% in the pre-intervention group; 75.6% in the during-intervention group) to 6–18 years (90.1% in the post-intervention group; H = 172.24, P < 0.001). Compared to the pre-intervention group, the post-intervention group had significantly higher rates of co-infection (45.4% vs. 6.7%; χ²=12.8, P < 0.001), consolidation detected by computed tomography (56.6% vs. 26.1%; χ²=56.2, P < 0.001), subpleural masses (34.9% vs. 13.4%; χ²=89.4, P < 0.001), and bronchoscopy utilization (34.9% vs. 3.7%; χ²=85.3, P < 0.001). Markers of inflammation, such as C-reactive protein (CRP), and myocardial injury markers, such as creatine kinase-MB (CK-MB), were also significantly elevated ( P < 0.05). The poor response rate to macrolides increased from 3.7% in the pre-intervention group to 34.9% in the post-intervention group (χ²=19.8, P < 0.001). Public health interventions caused a “suppression-rebound” effect in childhood Chlamydia pneumoniae (CP) pneumonia. This effect led to a shift in incidence toward school-aged children in Beijing. Following this rebound, post-intervention cases have shown more severe imaging findings and higher rates of macrolide unresponsiveness among CP pneumonia cases, which indicates the need for targeted school-based prevention and optimized antibiotic treatment. Not applicable.