Meteorological associations and clinical severity of pediatric Mycoplasma pneumoniae pneumonia hospitalizations at referral hospitals in climatically diverse regions of China, 2015–2025

Mycoplasma pneumoniae (MP) pneumonia exhibits seasonal and geographic variability, but meteorological influences on pediatric hospitalization patterns across different climatic regions remain uncertain. We conducted a multicenter retrospective study of 21,763 children aged < 18 years hospitalized with MP pneumonia at referral hospitals in five Chinese provinces in 2015-2025. Daily admissions were linked with ERA5 temperature and relative humidity. Province-specific distributed lag non-linear models, adjusted for trend, school vacations, holidays and the COVID-19 pandemic period, were pooled by meta-analysis and tested with negative-control exposures, case-crossover and false-discovery-rate analyses; mixed-effects models assessed severe disease. The median age was 4.1 years and 55.0% were male. Admissions peaked in October-December, with seasonality differing by province. Severe disease occurred in 17.4% (5.7-24.7% across four provinces), was most frequent at ≥6 years and increased after the pandemic (adjusted odds ratio 2.75, 95% CI 2.44-3.11). Pooled temperature and humidity associations were null in the main analysis and all robustness checks, and no province-specific association passed all checks. Severity of pediatric MP pneumonia increased substantially after the pandemic and was highest in school-aged children, whereas short-term weather showed no consistent effect once seasonal confounding was addressed. Surveillance should prioritize post-pandemic clinical changes over weather-based prediction.