2000至2012年臺灣水痘流行病學與疾病負擔

Abstract

背景及目標：水痘疫苗於1997年引進臺灣，1998、1999年起分別於台北市、台中市、台中縣提供年滿1歲幼兒公費接種，2004年起擴及全國。本研究分析國內自2000至2012年的水痘流行病學趨勢、水痘相關的住院率、併發症與死亡等疾病負擔，及水痘疫苗的保護效果，並估算醫療資源與社會成本耗用情形，做為評估水痘預防接種政策的參考。 方法：自全民健康保險研究資料庫選取2000至2012年間就醫紀錄曾有與水痘相關之國際疾病分類代碼者，另自預防接種資訊系統(national immunization information system, NIIS)取得水痘病人的水痘疫苗接種資料。使用「年齡—年代—世代 ( Age-Period-Cohort, APC )」分析方法，計算水痘發生率在不同年齡、年代、世代的變化趨勢，同時分析水痘相關住院、併發症、死亡、突破感染、醫療支出及社會成本耗損情形。 結果：隨著公費水痘疫苗接種政策普及全國年滿1歲幼兒，2012年水痘發生率已較2000年大幅下降87%，發生率高峰自3到5歲延後至10到12歲，平均感染年齡由7.92歲上升至16.25歲。較早實施公費疫苗接種政策的地區（早區），其發生率在2000年已有顯著下降，晚區在實施公費疫苗接種後，趨勢與早區逐漸接近。水痘病人住院率平均每千人15.51人，以未滿1歲嬰兒、20至29歲、30至39歲及70歲以上者較高，平均住院天數為4.76天。33.47%的住院病人有併發症，以下呼吸道感染最常見。有16名水痘病人死亡，其中37.5% (6/16)有潛在疾病，81.25% (13/16)出現併發症。突破感染的平均年齡為5.28歲，1999年至2006年的出生世代，接種水痘疫苗5年後的保護效果介於82.27%至94.78%。水痘醫療支出逐年降低，以5歲病人的醫療支出占比最高，住院支出於所有醫療支出的占比逐年上升至4成，水痘相關社會成本耗損約為醫療支出的8.28倍。投資1元於疫苗，可節省2.97元的醫療支出與社會成本。 結論：公費水痘疫苗接種政策已大幅降低感染與住院，有效減少醫療支出與社會成本耗損。在第2劑水痘疫苗導入幼兒常規接種之前，有潛在疾病的兒童及不具水痘免疫力的成人，若無疫苗接種禁忌，可考慮自費接種第2劑或兩劑水痘疫苗，有助於避免嚴重併發症的發生。

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.