BACKGROUND: Herpes Zoster (HZ) is a painful and costly reactivation of latent varicella virus in older adults. One vaccine is currently marketed in the US to prevent HZ, Zoster Vaccine Live (ZVL), and a non-live subunit adjuvanted candidate vaccine (HZ/su) is under regulatory review. Clinical literature suggests that waning of ZVL efficacy in previously vaccinated subjects may necessitate revaccination.
OBJECTIVE: To determine the cost-effectiveness of revaccination against HZ: HZ/su versus no vaccine and HZ/su versus ZVL in US adults previously vaccinated with ZVL aged 60+.
METHODS: The ZOster ecoNomic Analysis (ZONA) model is a deterministic Markov model. It followed a hypothetical 1 million(M)-person cohort of US adults aged 60+ previously vaccinated with ZVL (5 years prior) over their remaining lifetimes from the year of revaccination with annual cycle lengths. Three different HZ revaccination strategies were compared: no revaccination, revaccination with ZVL, and revaccination with HZ/su. The primary perspective was societal. Model inputs included residual ZVL efficacy, demographics, epidemiology, vaccine characteristics, utilities and vaccine costs. Costs and quality-adjusted life-years (QALYs) were presented over the lifetimes of the cohort from the year of revaccination and discounted 3% annually. Deterministic and probabilistic sensitivity analyses, along with scenario and threshold analyses, were carried out to explore the robustness of our findings considering uncertainty about model inputs.
RESULTS: The ZONA model estimated that in the 1M-person cohort, revaccinating with HZ/su would reduce disease burden compared to no revaccination, resulting in a gain of 1,633 QALYs at a total societal cost of $96M. This produced an incremental cost-effectiveness ratio of $58,793 per QALY saved. Compared to revaccinating with ZVL, the ZONA model estimated that revaccination with HZ/su would reduce disease burden, resulting in a gain of 1,187 discounted QALYs and a societal cost savings of almost $84M. Sensitivity, scenario, and threshold analyses demonstrated robustness of these findings.
CONCLUSIONS: Revaccination with HZ/su is a cost-effective strategy relative to no revaccination and cost-saving revaccination strategy relative to revaccination with ZVL in US adults aged 60+ who have been previously vaccinated against HZ. Results were robust as demonstrated by sensitivity, scenario, and threshold analyses.
