The Epidemiological Characteristics and Disease Burden of Varicella in Taiwan from 2000 to 2012
Date Issued
2016
Date
2016
Author(s)
Wang, En-Tzu
Abstract
Background and purpose: The varicella vaccine has been available in Taiwan market since 1997. Taipei City and Taichung City/County started providing one free dose of varicella vaccine to 1-year-old children in 1998 and 1999, and a mass varicella immunization program was established to provide free vaccination for all 1-year-old children throughout Taiwan. This study investigated the epidemiological characteristics and disease burden of varicella from 2000 to 2012. The results will be essential to refine our immunization policy. Method: Patients with varicella-related ICD-9-CM codes from the 2000-2012 National Health Insurance Database were included. Their immunization data was obtained from National Immunization Information System (NIIS). The Age-period-cohort (APC) analysis was used to calculate the age, period, and cohort-specific incidence of varicella. This study also investigated the geographic and seasonal distribution, hospital admission rate, breakthrough rate, vaccine effectiveness, medical costs and indirect costs from the societal perspective of varicella. Result: From 2000 to 2012, the implementation of a routine childhood varicella vaccination program has resulted in 87% decline in morbidity. The overall age-specific incidence peaked in pre-school children then shifted to teenagers, and the average age increased from 7.92 years to 16.25 years. In 2000, there was a significant decrease in incidence observed in areas implementing the free vaccination policy (early area). The deviance between early and late area had been narrowed after the implementation of the nationwide free vaccination program in 2004. The varicella-related hospital admission rate was 15.5/1000 patients. Infants younger than 1 year, adults aged from 20 to 39 years and older than 70 years had the highest admission rates. The complication rate among patients admitted to hospital was 33.47%, and the most common complication was lower respiratory tract infection. The mean duration of hospital stay was 4.76 days. 16 patients with varicella died, 37.5% had underlying disease and 81.25% had complication related to vericella. The mean age at breakthrough infection was 5.28 years. For birth cohorts 1999 to 2006, the vaccine effectiveness against varicella was 82.27% to 94.78% after five years of vaccination. The annual varicella-related medical expense declined after 2002 and the proportion of medical costs for admission has increased to 40%. The age-specific medical expenses peaked in 5-years old children. The indirect costs from the societal perspective of varicella were up to 8.28 times of medical costs. Every one dollar invested on the varicella vaccine saved 2.97 dollars of medical and social costs on average. Conclusion: The impressive decline in varicella morbidity, hospitalization, medical and social costs can be directly attributed to successful implementation of the 1-dose immunization program. A second-dose booster may be considered for children with underlying disease until the second dose introduced to routine childhood immunization program. Two-dose vaccination is also recommended for susceptible adults to prevent serious complications.
Subjects
varicella
varicella vaccine
epidemiology
breakthrough infection
vaccine effectiveness
disease burden
SDGs
Type
thesis
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