Duration of Antiviral Prophylaxis among Patients Receiving Autologous Hematopoietic Stem Cell Transplants (Auto-HSCT)

Background: Guidelines recommend up to 1 year of antiviral prophylaxis (AP) for patients receiving Auto-HSCT. There are no real world data on duration of AP or risk of herpes zoster (HZ) given AP duration in these patients. The objectives of this study are to describe AP agents and duration and to compare incidence of HZ by duration in Auto-HSCT patients.

Methods: This is a retrospective, observational study using MarketScan® Commercial and Medicare Supplemental databases. We included patients ≥18 years old who: 1) had Auto-HSCT procedure during 2009-2013; 2) had chemotherapy within 60 days prior to Auto-HSCT procedure (latest chemotherapy date being the study enrollment date); 3) were continuously enrolled in health plans for at least 1 year before and after the study enrollment date; 4) did not receive zoster vaccine; 5) did not have Herpes Simplex Virus or Cytomegalovirus Disease; 6) did not have HZ during 1 year before the study enrollment date; and 7) did not have HZ during 7 days before and/or after the first AP prescription. AP duration was the sum of total days supply of AP prescriptions from 30 days before to 365 days after the study enrollment date. All patients were followed from the study enrollment date to end of continuous health plan enrollment, death, or 12/31/2014 to assess HZ incidence. We used Poisson regression to estimate the 95% confidence interval (CI) of HZ incidence and Cox model to estimate time to HZ by AP duration.

Results: We identified 1,959 eligible Auto-HSCT patients. On average, patients were 56 years old (SD=11); 60% were male. 1,821 (93.0%) patients were prescribed AP. Acyclovir was the most common agent (78.1%). The average duration of AP was 220 days (SD=122). 198 (10.1%) patients had AP for≥1 year. HZ incidence was 42.4/1,000 person-years (PY) (95%CI=[36.5,49.0] for the overall cohort, and 55.7, 53.3, 41.2, 34.8, and 22.0/1,000 PY for patients with <90, 90-179, 180-269, 270-364, and≥365 days of AP (p<0.001), respectively (Figure).

Conclusion: Auto-HSCT patients are at increased risk for HZ, even when prescribed AP. A substantial portion of these patients have AP for <1 year, increasing their risk of HZ and its complications. A safe and effective vaccine against HZ for Auto-HSCT patients could be a useful adjunctive prevention strategy.