Risk Factors for Loss of Varicella Immunity After Pediatric Kidney Transplantation

Background: 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. Methods: 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, number of VZV vaccines received, and the interval between the last dose of VZV vaccine and Tx. Results: 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 ³3 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). Conclusion: 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.