Seroconversion following varicella vaccination in children and adolescents with nephrotic syndrome

Limited data exist on seroconversion rates post-varicella vaccination in children with idiopathic nephrotic syndrome (NS).

This cross-sectional study assessed anti-varicella IgG antibodies (VZV-IgG) in idiopathic NS children aged 1-18 years who were previously vaccinated (2 doses at a minimum 8-week interval), at least 3 months prior to enrolment. Exclusion criteria included secondary NS and eGFR < 60 mL/min/1.73 m² at the time of vaccination. Baseline characteristics and seroconversion titres (VZV-IgG ≥ 110 IU/L) by enzyme-linked immunosorbent assay (ELISA) kit were assessed.

Two-hundred children with idiopathic NS (55.5% males) received varicella vaccine. The median interval between doses was 3 months [IQR 2, 7], with a median age at vaccination of 6.8 years [3.8, 9.8], and a median illness duration of 4.1 years [1.7, 6.6]. Overall seroconversion rate was 64.5% with median VZV-IgG titres of 179 [IQR 62, 452] IU/L. The seroconversion was significantly associated with clinical phenotype when unadjusted for confounders. On univariate analysis, each additional relapse, children on levamisole post-vaccination, those on one second-line immunosuppressive agent, on two second-line immunosuppressive agents, and each additional month after vaccination were associated with 16%, 88%, 66%, 77%, and 3% significantly lower odds of seroconversion. The seroconversion rates or titres among those vaccinated within 4 weeks of discontinuation of steroids were however not significantly different. Breakthrough varicella occurred in 1.5%.

To conclude, this study demonstrates that varicella vaccination confers seroprotection in approximately two-thirds of children with NS, with low rates of breakthrough varicella.