Existing knowledge gaps: Nephrotic syndrome is treated with daily high dose corticosteroid therapy, followed by low-moderate dose corticosteroid therapy (lmCT - 1.5 mg/kg alternate day; 40 mg maximum dose). Indian guidelines mention to avoid live attenuated vaccines (LAV; measles, mumps, rubella [MMR] and/or varicella zoster vaccine [VZV]) till end of lmCT. However, most clinicians wait for 4 weeks after completion of therapy, leading to a missed opportunity for vaccination in this vulnerable cohort.

Novelty: This study will generate prospective data, on the immunogenicity and safety of LAV in NS in children at the end of low-moderate dose corticosteroid therapy, compared against the standard of care vaccination practice.

Objectives: Comparison of seroconversion to LAV at 4 weeks, in children with nephrotic syndrome, during the last 2 weeks of lmCT versus those administered LAV after 4 weeks of stopping lmCT.

Methods: Children >=1 year of age with NS, who present to the outpatient and inpatient departments, in remission of NS with lmCT, will undergo screening for seroprotection against varicella, mumps, measles and rubella. Immune response (humoral and cell-mediated) will be assessed in this population and randomized into early and standard interventions groups if found eligible. Early intervention group will receive LAV during the last 2 weeks of lmCT while standard intervention group will receive LAV 4 weeks after completion of lmCT, after obtaining written informed consent. Siblings of recruited children, or healthy children with no history of measles, mumps, rubella or varicella, and no detectable antibodies against any of these viruses, will be enrolled as healthy controls. Redosing of vaccine will be done to prevent waning of responses, at 12 weeks after first dose, (in remission of NS). Vaccine response titers will be assessed in all participants at 4, prior to 2^nd dose, 8 weeks after 2^nd dose and at 52 weeks, with all patients followed for 1 year. Adverse events occurring during the study period will be monitored and assessed by the Data Safety Monitoring Board. Prospective registration will be performed at Clinical Trials Registry of India and the Institutional Review Board.

Expected outcome: Safety and immunogenicity of LAV during lmCT (last 2 weeks of alternate day corticosteroid therapy) in children with NS can be established, which can be incorporated into Indian guidelines.