Budget-Impact Analysis of Alternative Herpes Zoster Vaccine Strategies: A U.S. HMO Perspective

BACKGROUND: A herpes zoster vaccine has been approved by the FDA for use in prevention of herpes zoster in individuals who are aged 50 years or older. The Advisory Committee on Immunization Practices (ACIP) recommends vaccination only in individuals who are aged 60 years and older. OBJECTIVES: To (a) estimate the overall budget and health impact of either the introduction of a new vaccination strategy (individuals over the age of 50 years vs. individuals over the age of 60 years) within a hypothetical health plan or simply an increase in coverage within the population aged 60 years and over and (b) discern what effect copayments and changes to copayments have on the health plan's budget. METHODS: A decision-analytic economic model was developed to inform managed care decision makers of the potential effect on costs and outcomes associated with the use of the herpes zoster vaccine for prevention of herpes zoster (i.e., simple zoster or shingles). The model took a U.S. payer perspective. The number of eligible patients entering the model was estimated by considering the age distribution of the plan population and the percentage of patients contraindicated for vaccination (i.e., those who were immunocompromised or who had a history of anaphylactic/anaphylactoid reaction to gelatin, neomycin, or any other component of the vaccine). Eligible patients were vaccinated based on the projected uptake rates among the unvaccinated population in 2 possible vaccination scenarios: (1) a vaccination strategy in which only individuals over age 60 years can be vaccinated and (2) a vaccination strategy in which individuals over age 50 years can be vaccinated. Vaccination was assumed to reverse the age-related decline in immunity against zoster. The population vaccinated each year was estimated based on the uptake rates (percentage of the eligible unvaccinated that are vaccinated) required to reach a target annual coverage (percentage ever vaccinated). Patients could experience costs and outcomes related to vaccination or related to herpes zoster. Specifically, vaccination could cause adverse events that would require the use of health care resources. Patients who developed zoster could experience postherpetic neuralgia or develop nonpain complications that would require the use of health care resources. Vaccine costs, zoster cases (with and without postherpetic neuralgia or nonpain complication), and vaccine-related adverse events for the 2 vaccination scenarios were estimated for each budget year. RESULTS: For a managed care organization population of 5 million members, the model estimated that a vaccination program that included patients over age 50 years instead of a program limiting vaccination to those over age 60 years was associated with a decrease in the number of patients developing zoster (2,372-3,392 cases avoided over 5 years). Annual incremental per-member-per-month (PMPM) costs associated with this vaccination program change were estimated to range from $0.08 to $0.14. When the vaccination program was kept at age 60 years and over and coverage was increased, the model estimated that the annual incremental PMPM costs ranged from $0.04 to $0.06. Differences in costs were driven primarily by vaccination costs. The results of the scenario analyses showed that lower vaccination costs because of the application of copayments for a managed care organization reduced the magnitude of the total cost increase associated with the increase in uptake. CONCLUSIONS: Vaccinating individuals aged 50 to 59 years with the herpes zoster vaccine would likely have an impact on a health plan's budget because of the expected increase in the total number of individuals being vaccinated in the population, with limited cost savings because of fewer cases of herpes zoster. Higher coverage of vaccinations resulted in a greater increase in total costs each year. However, increasing coverage would also result in a decrease in the number of individuals developing zoster and associated postherpetic neuralgia and nonpain complications over the next 5 years.