Abstract
INTRODUCTION: Herpes zoster (HZ, Shingles) is a vaccine-preventable viral disease impacting patients' quality of life owing to pain and rash. An estimated 15 million HZ cases occur annually in individuals aged ≥ 50 years worldwide. Recombinant zoster vaccine (RZV) is effective in protecting against HZ. This is the first study evaluating the potential incremental public health benefits in terms of HZ cases averted worldwide by vaccinating adults aged ≥ 50 years with RZV. METHODS: A previously published static multi-cohort Markov model with an annual cycle length and lifetime horizon was used for all analyses. Demographic data depicting populations on 31 December 2023, and age-sex specific mortality rates by region were sourced from United Nations (2022). HZ incidence rates were informed from a recent meta-regression analysis of global HZ burden (Asia, Europe, Northern America, Oceania, and worldwide). RZV efficacy and waning modelling was based on 11-year clinical trial follow-up data [NCT02723773]. RESULTS: Assuming 70% second-dose compliance in the general population aged ≥ 50 years worldwide, increased RZV uptake by 5% reduced the number of expected HZ cases by > 10 million over the vaccinated cohort's remaining lifetime. More than 5 million of the averted cases were among the cohort vaccinated at ages 50-59 years. Numbers needed to vaccinate (NNV) to avert one HZ case worldwide ranged from 9 at 50-59 years to 18 at ≥ 80 years-of-age, with an overall NNV of 10 for the entire cohort aged ≥ 50 years. Variations observed by region and vaccination age reflected varying inputs, i.e., population counts, HZ incidence rates, mortality rates, and vaccine efficacy waning by age. CONCLUSIONS: A modest (5%) increase in absolute RZV uptake worldwide was estimated to avert millions of additional HZ cases. Lower NNVs were observed in younger vaccinated cohorts irrespective of region, outlining the merits of long-term protection afforded by RZV, and suggesting that earlier vaccination with RZV may be a more effective public health policy against HZ. Greater numbers of averted HZ cases and lower NNVs estimated at ideal second dose compliance demonstrated the importance of timely series completion.