DETERMINING THE OPTIMAL AGE TO VACCINATE AGAINST HERPES ZOSTER: A COST-EFFECTIVENESS ANALYSIS

Determining the optimal age to vaccinate against herpes zoster:

a cost-effectiveness analysis

Purpose:

The advisory Committee on Immunization Practice (ACIP) recommends the live attenuated herpes zoster (HZ) vaccine for all people aged ≥ 60 years, but the optimal time to vaccinate is unknown. We aimed to determine the optimal age to administer a once-per-lifetime HZ vaccine among immunocompetent adults ≥ 60 years using cost-effectiveness analysis.

Method:

 

We employed a Markov decision model to assess the costs and effectiveness from the societal perspective of 22 vaccination strategies: no vaccination, and one-time vaccination at various ages in one-year increments from 60-80 years. The entire cohort started in the ‘Healthy' state at age 60, then transitioned between HZ-related health states until death or age 120. Transition probabilities were drawn from the medical literature. The burden of HZ, postherpetic neuralgia, and other complications (ophthalmic and otic sequelae, hospitalization and death) among vaccinated adults was reduced in proportion to vaccine efficacy, which declined over time. Vaccine efficacy and its duration were based on the Shingles Prevention Study and recently published long-term follow-up data. Other model inputs including the epidemiology, utilities, and costs were derived primarily from US-based studies. Costs included direct medical and indirect costs in 2014 $; effectiveness was expressed in quality-adjusted life years (QALYs). Costs and effectiveness were discounted at 3% per year. Incremental costs per QALY gained were calculated for non-dominated strategies. Scenario analyses assuming higher initial efficacy and longer duration were conducted. Probabilistic sensitivity analysis was employed with 10,000 Monte Carlo simulations.

Result:

No vaccination had the lowest cost and produced the fewest QALYs. Vaccination at age 70 produced the most QALYs with incremental costs of $39,178/QALY. Vaccination before 70 produced fewer QALYs at higher cost. Vaccination after 70 cost less, but had higher ICERs than vaccination at age 70. Results were insensitive to plausible vaccine efficacy and duration estimates in scenario analyses. At a willingness-to-pay threshold of $100,000/QALY, vaccination at age 70 had 99% probability of being most cost-effective.

Conclusion:

One-time HZ vaccination appears to achieve maximum benefits and be most cost-effective at age 70. Revising the ACIP's recommendation to begin vaccination at 70 should provide greater benefit at lower cost.