Investigating the efficacy and mechanisms of Qingfei Tongluo Formula in the treatment of children with MP infection combined with CVA based on Th17/Treg immunological balance

INTERVENTION: Treatment group:Western medicine basic treatment + Chinese herbal medicine Lung‐Clearing and Meridian‐Connecting Formula;Control Group:Western medicine basic treatment +placebo; CONDITION: Mycoplasma pneumoniae infection and cough‐variant asthma PRIMARY OUTCOME: Daytime and Nighttime Cough Visual Analog Scale (VAS);Mycoplasma pneumoniae DNA(MP‐DNA) conversion rate; SECONDARY OUTCOME: Pulmonary Function;Exhaled Nitric Oxide (FeNO);TCM Syndrome Score;Serum cytokines (IL‐17A, IL‐6, IL‐10, TGF‐ß);The proportion of Th17 and Treg cells in peripheral blood.; INCLUSION CRITERIA: The participants must meet the following criteria simultaneously: Meet the following conditions simultaneously: (1) Aged 5 ‐ 14 years old, regardless of gender; (2) Meet the diagnostic criteria for Mycoplasma pneumoniae (MP) infection in children (symptoms of acute respiratory tract infection, and positive serum MP ‐ IgM or positive MP ‐ DNA PCR test of nasopharyngeal swab); (3) Meet the diagnostic criteria for cough variant asthma (CVA) in children (persistent cough > 4 weeks, often accompanied by nocturnal or early ‐ morning attacks, positive bronchial provocation test or effective anti ‐ asthma treatment); (4) Cough visual analogue scale (VAS) score = 30mm; (5) Meet the diagnostic criteria for wind ‐ heat cough or phlegm ‐ heat cough in traditional Chinese medicine (cough, yellow phlegm, discomfort in the throat, nasal congestion, yellow or turbid nasal discharge, red tongue with thin yellow or yellow greasy coating, floating and rapid or slipp