BACKGROUND: Herpes zoster (HZ), commonly referred to as shingles, is a reactivation of latent varicella zoster virus in patients previously infected. Clinical characteristics of HZ include painful rash with potential complications, including post herpetic neuralgia (PHN). Care for HZ and PHN incurs significant costs and vaccination is beneficial. The aim of this study was to compare the impact on HZ and PHN case avoidance of two HZ vaccines, an available live-attenuated zoster vaccine (zoster vaccine live [ZVL]) versus a candidate non-live adjuvanted HZ subunit vaccine (HZ/su), in the US population.
METHODS: A Markov model called ZONA (ZOster ecoNomic Analyses) was developed following two age cohorts (≥60 years to represent the current ACIP recommendation and ≥65 years to represent the Medicare population) over their lifetimes from the year of vaccination. Demographic data were obtained from the US Census, whereas HZ incidence and the proportion of HZ individuals developing PHN were derived from published US-specific sources. Age-specific vaccine efficacy and waning rates were based on published clinical trial data. Vaccine coverage for both vaccines was assumed to be 30.6% and 34.2% in the two age cohorts, respectively, based on CDC data; compliance of the second dose of the HZ/su vaccine was 69%, based on data from clinical trials and Hepatitis B 2nd dose completion. Sensitivity analyses demonstrated robustness of the base analysis findings.
RESULTS: In the US, for cohorts of 66.83 million (M) persons aged 60+ and 47.76M aged 65+ it was estimated that the HZ/su vaccine would reduce the number of HZ cases by 2.12M and 1.55M in the two age cohorts, respectively, compared to 0.65M and 0.45M using the ZVL. Furthermore, the HZ/su vaccine would reduce the number of PHN cases by 0.23M and 0.18M in the two age cohorts, respectively, compared to 0.10M and 0.09 using the ZVL. The number needed to vaccinate to prevent one HZ case were 10 and 11, in the respective cohorts, using the HZ/su vaccine compared to 31 and 37, in the respective cohorts, using the ZVL.
CONCLUSIONS: Due to higher and sustained vaccine efficacy, the candidate HZ/su vaccine demonstrated superior public health impact in the US compared to the currently available ZVL.
