Varicella-zoster reactivation after allogeneic stem cell transplantation without routine prophylaxis--the incidence remains high.

One-year prophylaxis with acyclovir has been shown to effectively prevent varicella-zoster virus (VZV) reactivation after allogeneic hematopoietic stem cell transplantation (HSCT) in a cohort that underwent transplantation in the beginning of the 2000s. Transplantation procedures have since changed considerably and reduced-intensity conditioning (RIC) is nowadays common. We investigated VZV reactivation without routine prophylaxis in a cohort of HSCT patients, 50% of whom had received RIC. The cumulative 2-year incidence of VZV reactivation was 20.7%. Risk factors in a multivariate analysis were treatment with mesenchymal stromal cells (relative hazard [RH], 1.65; confidence interval [CI], 1.07 to 2.54; P = .02), total body irradiation ≥6 Gy (RH, 1.55; CI, 1.14 to 2.13; P = .006), engraftment later than day 16 (RH, 1.46; CI, 1.07 to 2.00; P = .02), and age 0 to 19 years (RH, 1.68; CI, 1.21 to 2.35; P = .002). There was no difference in VZV reactivation between patients receiving myeloablative conditioning or RIC. VZV-related complications occurred in 29% of the patients with reactivation; most common were disseminated disease and postherpetic neuralgia. No single low-risk group for VZV reactivation could be identified. We conclude that VZV reactivation remains common after HSCT and carries a high complication rate, warranting prophylaxis.