PURPOSE: 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, such as post herpetic neuralgia (PHN). It has been estimated that the annual cost burden of HZ in the United States (US) will increase from $628 million (M) in 2005 to $4. 7 billion (B) in 2030; however, prevention of HZ is obtainable via vaccination. The aim of this study was to compare the potential impact on HZ and PHN case avoidance of two independent HZ revaccination strategies versus no revaccination.
METHODS: A Markov model called ZONA (ZOster ecoNomic Analyses) was developed to follow the remaining lifetimes of patients aged 65 years and older who were previously vaccinated with a live-attenuated zoster vaccine (ZVL, Zostavax) five years earlier. Choices modeled were revaccination with a non-live subunit vaccine (HZ/su, Shingrix) versus no revaccination and revaccination with ZVL vs no revaccination. Individuals progressed through potential health states including healthy, HZ, PHN, natural and HZ-related death, and recurrent HZ health states. Demographic data were obtained from the US Census, along with CDC data to estimate the portion of this population previously vaccinated with ZVL (34. 2%). Coverage for revaccination strategy was varied from 30% to 100%. Compliance for the second dose of the HZ/su vaccine was 69%. The incidence of HZ 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 and persistence data. Incremental HZ and PHN case avoidance and numbers needed to vaccinate to avoid one HZ and then one PHN case were calculated.
RESULTS: For the 16. 33M US adults aged 65 years and older whom were previously vaccinated with ZVL, it was estimated that the HZ/su revaccination strategy would reduce HZ by 385 thousand (K) [30% coverage] to 1. 28M [100% coverage] cases, compared to 70K to 232K cases from receiving ZVL, respectively over the individual's estimated lifetimes. Furthermore, HZ/su would reduce PHN by 40K to 134K cases, compared to 12K to 39K cases using ZVL. The number needed to revaccinate with HZ/su to prevent one HZ case was 13 compared to 71 people with ZVL. The number needed to revaccinate to prevent one PHN case was 123 for HZ/su compared to 421 for ZVL.
CONCLUSION: Due to higher and more sustained vaccine efficacy, the HZ/su vaccine demonstrated superior case avoidance for HZ and PHN in the US as compared to the currently available ZVL when revaccinating patients aged 65 years and older previously vaccinated with ZVL.
