Low-Dose Acyclovir Reduces the Reactivation of Herpes Simplex and Varicella Zoster Viruses After Allogeneic Stem Cell Transplantation.

INTRODUCTION

Reactivation of herpes simplex virus (HSV) and varicella zoster virus (VZV) is a potential complication following allogeneic stem cell transplantation (alloSCT). Since different doses and durations of acyclovir prophylaxis may be utilized across transplant centers, this study aimed to evaluate the effectiveness of a lower dose of acyclovir in preventing HSV and VZV reactivation in alloSCT recipients within our institution.

METHODS

A retrospective chart review was conducted for patients who underwent alloSCT between April 2016 and May 2023. Patients received acyclovir 400 mg orally twice daily as prophylaxis, starting before stem cell infusion and continuing for two years after alloSCT, with ongoing use while on immunosuppressive therapies. Outcomes measured include incidence of HSV and VZV reactivation, timing of viral reactivation, acyclovir-related adverse events, and hospitalizations due to viral reactivation. Pertinent data collected were risk factors for viral reactivation in patients such as immunosuppressive therapies and chemotherapy regimens. Descriptive statistics were used for data analysis.

RESULTS

A total of 246 patients were included in this study. The majority of patients were male with a median age of 60 years (range 20-76) and a diagnosis of acute myeloid leukemia. HSV reactivation occurred in 10 out of the 246 patients (4%) and none had VZV reactivation. The median time to HSV reactivation was 100 days (range 10-1400). No patient had acyclovir-related adverse events such as acute kidney injury, neurotoxicity, or rash. Hospitalization related to HSV reactivation occurred in four of the 10 affected patients (40%).

CONCLUSIONS

Oral acyclovir 400 mg taken twice daily for prophylaxis in alloSCT recipients is both effective and well-tolerated. This lower-dose regimen effectively prevents HSV and VZV reactivation without compromising efficacy or patient safety.