Syndrome differentiation treatment of Traditional Chinese Medicine reduces the re-hospitalization rate of discharged elderly patients with COVID-19 infection: a prospective, multicenter, double-blind, randomized controlled study

INTERVENTION: treatment group:Shenqi Baofei prescription or Shenmai Baofei prescription;control group:Shenqi Baofei prescription placebo or Shenmai Baofei prescription placebo; CONDITION: COVID‐19 infection PRIMARY OUTCOME: Readmission rate; SECONDARY OUTCOME: mortality;Clinical symptom score;dyspnea scores;6 minutes' walk distance;Pulmonary Function Testing;Chest CT imaging;SF‐36, Medical Outcomes Study 36‐item Short Form Health Survey;Patient Health Questionnaire‐9 (PHQ‐9);7 items of General Anxiety Disorder (GAD‐7); Pittsburghsleepqualityindex;The post‐traumatic stress disorder cheeklist (PCL‐C);Safety observation index; INCLUSION CRITERIA: 1. Elderly patients with COVID‐19 infection (medium/severe/critical type) who meet the diagnostic criteria and classification within 1 week after discharge; 2. It is consistent with the syndrome differentiation of Qi deficiency and phlegm‐dampness (lung qi deficiency, phlegm‐dampness not exhausted), Qi Yin deficiency and phlegm‐heat syndrome (Qi Yin deficiency, phlegm‐heat not clear); 3. Aged >= 65 years; 4. At least one or more symptoms (cough, phlegm, fever, conscious fever, shortness of breath/dyspnea, chest pain, headache, palpitation, fatigue/fatigue, sleep disorders, cognitive dysfunction, activity restriction, reduced taste/loss, decreased smell/loss, poor appetite, diarrhea, etc.) were reported within 12 hours before screening. 5. Pulmonary CT imaging is not completely absorbed; 6. Voluntary treatment and oral medication; 7. Sign the informed consent form.