Disease burden and epidemiology of herpes zoster in pre-vaccine Taiwan
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.
Section snippets
Data collection
Taiwan's NHI covered most of the health care costs for 98% of its 22.9 million people in 2006 [5], and its database contains health care data to Bureau of NHI by more than 95% of Taiwan's hospitals, which contracted by NHI to care for its residents. NHI covered the physician fee, nurse fee, ward fee of 3-bed wards, pharmacist fee, laboratory and radiographic examinations, prescription medicines, and all the medical procedures or treatment for both inpatients and outpatients. The expense of
Age distribution and age-specific annual incidence
There were a total of 6,72,782 patients with zoster during the study period. Fig. 1 shows that the age-specific case numbers and cumulative percentage of herpes zoster. Thirty-four percent of the cases were between 40 and 60 years old with 63% of the cases being older than 40 years. We found no significant seasonal variation in incidence. The overall annual incidence of herpes zoster during 2000–2005 in Taiwan was 4.97 (95% CI, 4.96–4.98) cases per 1000 people. Fig. 2 shows the age-specific
Discussion
This study characterizes the epidemiology of herpes zoster in Taiwan in a pre-vaccine era. The incidence of herpes zoster, which was 4.97 per 1000 overall, increased with age peaking at 11.77 per 1000 in the people older than 70 years old. The elderly over 70 years old also had significantly higher hospitalization, ICU care, and higher medical costs per patient compared to the other age groups.
We found an overall annual incidence for Taiwan to be 4.97 per 1000, a higher incidence than reported
Acknowledgments
This work was supported by the grant (DOH98-DC-1010) from the Department of Health, Taiwan. Conflict of interest statement: There is no conflict of interest for all authors.
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