Low-Dose Acyclovir Prophylaxis for Varicella zoster Reactivation in Autologous Hematopoietic Cell Transplantation Recipients

Varicella zoster virus (VZV) reactivation after autologous hematopoietic cell transplantation (auto-HCT) may be observed in a quarter of patients. Currently, prophylactic use of acyclovir 800 mg twice daily or valacyclovir 500 mg twice daily is recommended for prophylaxis against VZV reactivation for at least one-year post-HCT, with continued use recommended in immunosuppressed recipients. Acyclovir dosing regimens vary between institutions despite the noted recommendations. In this single-center, retrospective study, recipients of auto-HCT who received at least one year of low-dose antiviral prophylaxis defined as the equivalent of acyclovir 400 mg orally twice daily or valacyclovir 500 mg daily were included. The primary objective of this study was to assess the incidence of VZV reactivation with low-dose acyclovir/valacyclovir prophylaxis in autograft recipients. One hundred and eighty patients undergoing auto-HCT between April 2008 and March 2015 were included. Patients received low-dose acyclovir, for a median duration of 55.5 months (range 12–100). There were no occurrences of VZV reactivation while patients were on these drugs. However, 2 patients (1.1%) had VZV reactivation after discontinuation of therapy, occurring 18.8 and 14 months from transplant and 6.7 and 2 months after stopping prophylaxis, respectively. Our retrospective analysis found low-dose antiviral prophylaxis with oral acyclovir 400 mg twice daily or valacyclovir 500 mg daily to be effective in preventing VZV reactivation in auto-HCT recipients.