Disease burden and epidemiology of herpes zoster in pre-vaccine Taiwan

Abstract

Herpes zoster, a common disease, has an important impact on the health of adults, particularly the elderly, and the health system. This study evaluated the disease burden and epidemiological characteristics of herpes zoster in Taiwan. Using herpes zoster-related ICD-9-CM codes used on Taiwan's National Health Insurance claims, we analyzed overall and age group differences in incidence, complications, utilization of healthcare facilities, lengths of stay, and cost of their medical care in Taiwan's population from 2000 to 2005. The overall annual incidence of zoster was 4.97 cases per 1000 people, with women having a significantly higher incidence than men (5.20 per 1000 vs. 4.72 per 1000, p < 0.001). The incidence increased stepwise with age, with 5.18 cases per 1000 in people 40–50 years old, 8.36 in those 50–60, 11.09 in those 60–70, and 11.77 in those above 70 years old. The estimated lifetime risk of developing herpes zoster was 32.2%. Zoster-related hospitalizations and medical cost per patient increased with age. In conclusion, about two-thirds of Taiwan's zoster cases occur in adults older than 40 years old and about one-third of the population would develop zoster within their lifetime.

Introduction

Herpes zoster results from a reactivation of latent varicella-zoster virus (VZV) infection and occurs decades after primary VZV infection as the people infected with this virus age and their cellular immunity wanes [1], [2]. This common disease has an important impact on the health of adults, particularly the elderly, and the world's health systems. The lifetime risk for zoster can be as high as 28% in Canada and 30% in United Kingdom [3]. The disease burden and medical expenses are greater for herpes zoster than those for varicella (chicken pox), which often occurs as result of initial primary VZV infection [4].

Since the development of the herpes zoster vaccine, many countries are considering implementing zoster vaccination programs. In order to design effective vaccination strategies and compare post-vaccination trends, it is important to characterize the epidemiology of herpes zoster at baselines locally. Although there were several studies on the epidemiology of zoster, most were based on database of people with certain medical insurance rather than nationwide population study. Those studies might ignore people of medical disadvantage and underestimate the incidence of zoster. Taiwan's National Health Insurance (NHI) is a program that covers the medical care of 98% of its population [5], so it almost covers its whole population. NHI is different from the medical insurance of the other countries in that almost all people can afford it and even if some people of low social economics cannot afford it, Taiwan government will pay for them. Therefore no matter how much people's income is, almost all the people in Taiwan receive the same health insurance. In this study, we used claims data from the Taiwan's National Health Insurance (NHI) to investigate the age-specific annual incidences, complication, hospitalization rates as well as healthcare utilization and medical expense related to herpes zoster in Taiwan from 2000 to 2005. The findings of such a study may provide information important to the development of future zoster vaccination policies.