Inclusion Criteria:  1. Children between 1 and 18 years with Steroid-Sensitive Nephrotic Syndrome. 2. Estimated glomerular filtration rate (eGFR) ≥90 ml/min per 1.73 m2 at study entry.  3. Remission at study entry. 4.No immunosuppressive agents have been used within 3 months of enrollment, except for the use of corticosteroid to treat nephrotic syndrome.  5. Provision of consent by a legal representative (parents or legal guardians) using a document approved by the institutional review board after receiving an adequate explanation regarding the implementation of this clinical trial. For children/youth ages 10-18, written assent is required using age-appropriate and background-appropriate documents.  Exclusion Criteria:  1.Diagnosis of secondary NS 2.Patients showing one of the following abnormal clinical laboratory values: leukopenia (white blood cell count ≤3.0*109/L); moderate and severe anemia (hemoglobin <9.0g/dL); thrombocytopenia (platelet count <100*1012/ L); positivity of autoimmunity tests (ANA, Anti DNA antibody, ANCA) or reduced C3 levels; Positive for hepatitis B surface (HBs) antigen, HBs antibody, hepatitis B core (HBc) antibody, or hepatitis C virus (HCV) antibody ; Positive for HIV antibody; Alanine aminotransferase (ALT) > 2.5× upper limit of normal value. Aspartate aminotransferase (AST) > 2.5× upper limit of normal value.  3. Presence or history of severe or opportunistic infections within 6 months before assignment; Presence of active tuberculosis or with a history of tuberculosis or in whom tuberculosis is suspected; Presence or history of chronic active infections such as Epstein-Barr virus and CMV virus; presence or history of active hepatitis B or hepatitis C or hepatitis B virus carrier. Presence of human immunodeficiency virus (HIV) infection or other active viral infections.  4. History of angina pectoris, cardiac failure, myocardial infarction, or serious arrhythmia，or poorly controlled hypertension 5. Presence or history of autoimmune diseases or vascular purpura. 6. Presence or history of malignant tumor 7. History of organ transplantation (excluding corneal and hair transplants). 8. Patients with a known allergy to steroid and their excipients or to Broncho-Vaxom 9. Assessed to be unfit for participation by the investigators