# Risk factors for loss of Varicella immunity after pediatric kidney transplantation

## TL;DR

This study finds that younger age and steroid use increase the risk of losing varicella immunity after kidney transplants in children.

## Contribution

Identifies specific risk factors for loss of varicella immunity in pediatric kidney transplant recipients.

## Key findings

- 24.4% of patients lost VZV immunity post-transplant, with younger age being a significant risk factor.
- Patients on steroid-based immunosuppression were more likely to lose VZV immunity.
- Receiving three or more VZV vaccine doses or vaccination within a year of transplant increased the risk of antibody loss.

## Abstract

Varicella zoster (VZV) vaccination pre-kidney transplant (Tx) can help prevent severe disseminated VZV in immunosuppressed recipients; however, studies have shown loss of humoral immunity post-Tx.

A retrospective analysis of 45 pediatric kidney Tx recipients with positive pre-Tx VZV IgG (>1.09 index). VZV IgG was assessed annually and compared with the induction agent used, the number of VZV vaccines received, and the interval between the last dose of VZV vaccine and Tx.

Median age at Tx was 16.7 years (IQR 12.7–18.5). 11 of 45 (24.4%) patients lost immunity to VZV at a median of 12.6 months post-Tx. Those who lost VZV immunity were younger at the time of Tx, 12.4 years vs. 17.3 years (P = 0.05) and more likely to be on steroid-based immunosuppression 81.8% vs. 32.4% (P = 0.006). There were no differences between the induction agents used and the ability to maintain VZV IgG antibodies. Subjects who required ≥3 doses of VZV vaccine to develop VZV IgG seropositivity were at a higher risk for losing their anti-varicella antibody post-Tx (HR 3.81, 95% CI 1.09–13.30, P = 0.04). Receiving VZV vaccination <1 year prior to kidney Tx was associated with a higher risk for losing anti-varicella antibody after Tx (HR 6.97, 95% CI 2.08–23.34).

In this small cohort, pediatric kidney Tx recipients are more likely to lose VZV IgG in those who were younger at the time of Tx, on steroid-based immunosuppression, required 3 or more doses of VZV vaccination to seroconvert, or received VZV vaccine <1 year before Tx.

A higher resolution version of the Graphical abstract is available as Supplementary information

A higher resolution version of the Graphical abstract is available as Supplementary information

The online version contains supplementary material available at 10.1007/s00467-025-07022-7.