Cost Effectiveness of Herpes Zoster Vaccine in Canada

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Abstract
Background: Herpes zoster (HZ), or shingles, results from reactivation of latent varicella zoster virus in the sensory ganglia of adults, and results in significant morbidity in the elderly, including the development of postherpetic neuralgia (PHN). The lifetime risk of HZ is about 20–30% and the incidence increases with age. The protective effect of the HZ vaccine has been shown in a large clinical trial; however, the effectiveness of the vaccine decreased with age of vaccination. Objective: We sought to compare the incremental cost and health benefits of HZ vaccine over status quo (no HZ vaccine) from the perspective of the Canadian healthcare payer. Methods: We developed a discrete-event simulation model comparing the costs and QALYs accrued to patients receiving HZ vaccine to those who did not. The effect of the vaccine on the (i) incidence of severe, moderate or mild HZ; (ii) severity and duration of HZ; (iii) incidence of PHN among patients with HZ; (iv) duration of PHN; and (v) costs associated with treating HZ and PHN were modelled. Data from published literature, including the Shingle Prevention Study, were used for transition probabilities. Health resource utilizations were estimated using administrative data retrieved from the British Columbia Medical Services Plan and hospital separation databases in British Columbia from 1994 to 2003. Utility estimates were obtained from various published sources. Canadian 2008 costs were used and both cost and QALYs were discounted at a 5% annual rate in the base-case analyses. Results: On average, receiving the vaccination lowered mean direct medical costs (excluding the vaccine costs) by $Can35 per person. The incremental cost and QALYs per person receiving the vaccine versus no vaccination were $Can115 and 0.0028 QALYs, respectively, resulting in an incremental cost-effectiveness ratio of $Can41 709 per QALY gained for a cohort of elderly subjects aged ≥60 years. Results were robust in probabilistic and univariate sensitivity analyses. Expected value of perfect information was estimated at $Can47.72 per person, reflecting the expected monetary losses that could be avoided by having perfect information on all model parameters. Conclusion: HZ vaccination of adults, especially for individuals aged 60–75 years, seems to be a cost-effective intervention and might be considered by Canadian decision makers.