Herpes zoster incidence and cost in patients receiving autologous hematopoietic stem-cell transplant

Objective: Among patients receiving autologous hematopoietic stem cell transplant (Auto-HSCT), we estimated the incidence of herpes zoster (HZ), compared health care costs among patients with and without HZ, and evaluated antiviral prophylaxis (AP) use.

Research Design and Methods: We conducted a retrospective study using data from a large health plan to identify patients ≥18 years with ≥1 claim for an Auto-HSCT procedure during 2006-2011 (N = 2,530). Patients were followed from date of Auto-HSCT until risk-end date, defined as development of HZ, end of enrollment, death, or 12/31/2011. HZ incidence was calculated as cases observed after Auto-HSCT divided by accrued time-at-risk in person-years (PY). AP use and duration were defined by prescription fills. One-year medical and pharmacy costs were calculated as combined health plan and patient paid amounts.

Main outcome measures: HZ incidence and health care costs were calculated using administrative claims data.

Results: Overall HZ incidence was 62.2/1000 PY (95% CI 54.3-70.9). Most (72.3%) patients were prescribed AP. During the first 90-days post-Auto-HSCT, patients without AP had increased incidence (151.6/1000 PY, 95% CI 88.3-242.6) compared to those prescribed AP pre- (30.9/1000 PY, 95% CI 11.3-67.2) or post-Auto-HSCT (33.0/1000 PY, 95% CI 13.3-67.9). Total adjusted mean one-year all-cause healthcare costs were $74,875 for patients who developed HZ and $70,279 for patients who did not (difference $4,596 (cost ratio: 1.07, 95% CI: 0.86-1.32, p = 0.566)).

Conclusions: HZ incidence was high despite AP use. Mean annual health care costs were higher for patients with HZ but the difference was not statistically significant. An effective vaccine against HZ could be useful in decreasing both incidence of and cost for HZ in this population.