Seroprevalence of varicella antibodies in unvaccinated children with nephrotic syndrome in disease remission.

Background and objectives Varicella-zoster (VZV) virus infection can be severe in children with nephrotic syndrome. Lack of varicella vaccination through the national immunisation programme in India leaves many vulnerable to infection. We conducted this study to document the seroprevalence of Varicella antibodies in patients with nephrotic syndrome. Methods This cross-sectional study (Oct 2024-May 2025) was conducted at a tertiary-care teaching hospital in India, in children (1-18 y) with nephrotic syndrome (both steroid-sensitive and steroid-resistant) in disease remission. Serum VZV IgG antibodies were measured using the EUROIMMUN ELISA kit; titres ≥100 IU/L were considered seroprotective. Results 100 patients were enrolled (median age 8 y). None had received varicella vaccination, and only two reported prior infection. Overall seroprotection was 22% with a geometric mean titre of 9.472 IU/L [median (IQR) 7.59 (3.35; 73.38) IU/L]. No significant difference was observed in titres between steroid-sensitive and steroid-resistant nephrotic syndrome (P=0.532), but seroprotection increased with age (11.1% in <5 y to 33.3% in >10 y). Interpretation and conclusions Low seroprevalence likely reflects the inadequacy of natural immunity and absence of routine varicella vaccination, warranting larger seroprevalence studies and future research on the need for priority immunisation for this high-risk population.