Cost-effectiveness of a vaccine to prevent herpes zoster and postherpetic neuralgia in older adults

Background: The Shingles Prevention Study showed that a varicella-zoster virus (VZV) vaccine administered to adults 60 years of age or older reduced the incidence of herpes zoster from 11.12 to 5.42 cases per 1000 person-years. Median follow-up was 3.1 years, and relative risk reduction was 51.3% (95% CI, 44.2% to 57.6%). Objective: To assess the extent to which clinical and cost variables influence the cost-effectiveness of VZV vaccination for preventing herpes zoster in immunocompetent older adults. Design: Decision theoretical model. Data Sources: English-language data published to March 2006 identified from MEDLINE on herpes zoster rates, vaccine effectiveness, quality of life, medical resource use, and unit costs. Target Population: Immunocompetent adults 60 years of age or older with a history of VZV infection. Time Horizon: Lifetime. Perspective: U.S. societal. Interventions: Varicella-zoster virus vaccination versus no vaccination. Outcome Measures: Incremental quality-adjusted survival and cost per quality-adjusted life-year (QALY) gained. Results of Base-Case Analysis: By reducing incidence and severity of herpes zoster, vaccination can increase quality-adjusted survival by 0.6 day compared with no vaccination. One scenario in which vaccination costs less than $100000 per QALY gained is when 1) the unit cost of vaccination is less than $200, 2) the age at vaccination is less than 70 years, and 3) the duration of vaccine efficacy is more than 30 years. Results of Sensitivity Analysis: Vaccination would be more cost-effective in "younger" older adults (age 60 to 64 years) than in "older" older adults (age >= 80 years). Longer life expectancy and a higher level of vaccine efficacy offset a lower risk for herpes zoster in the younger group. Other factors influencing cost-effectiveness include quality-of-life adjustments for acute zoster, unit cost of the vaccine, risk for herpes zoster, and duration of vaccine efficacy. Limitations: The effectiveness of VZV vaccination remains uncertain beyond the median 3.1-year duration of follow-up in the Shingles Prevention Study. Conclusions: Varicella-zoster virus vaccination to prevent herpes zoster in older adults would increase QALYs compared with no vaccination. Resolution of uncertainties about the average quality-of-life effects of acute zoster and the duration of vaccine efficacy is needed to better determine the cost-effectiveness of zoster vaccination in older adults.