2018至2019年臺灣麻疹流行病學及臨床特徵

Abstract

背景及目的： 2018及2019年全球多國爆發麻疹疫情，臺灣亦受國際疫情影響，確診病例超越過往數十年紀錄，本研究目的為探究臺灣麻疹政策推行40年後，對麻疹發生率之影響，進一步從確診個案流行病學與實驗室診斷資訊，找出罹病危險因子或個案特徵，提供臨床與公共衛生防治參考。 方法：本研究以衛生福利部疾病管制署「傳染病個案通報系統」中，於2002至2019年發病之麻疹確定病例進行回溯性世代研究(retrospective cohort study)，並參考麻疹疫苗常規接種計畫分為3個世代，包含(1) Cohort A (1976年9月以前出生，非疫苗受惠世代)、(2) Cohort B (1976年9月-1990年9月出生，應接種2劑MV疫苗及1劑MMR疫苗)，及(3) Cohort C (1990年9月以後出生，應接種2劑MMR接種)。基本人口學變項由「傳染病個案通報系統」資料取得，分析2018至2019年麻疹確定個案病程發展、疫苗接種史、接觸史、旅遊史等類別變項，進行卡方檢定或費雪精確性檢定。 結果：2002至2019年麻疹確定病例共計397例，其中以Cohort B(1976-1990年出生)且年齡介於18-39歲間病例最多(178人, 44.8%)，為臺灣近18年麻疹防治負擔最大標的族群。另分析2018至2019年共計168名麻疹確定病例臨床表現，主要為發燒(89%)及紅疹(95%)，但仍有49%無咳嗽、鼻炎或結膜炎等任一種症狀，紀錄有柯氏斑症狀比率偏低(8%)。83%病例源自境外移入及境外移入衍生群聚；60%為醫師通報、37%經過接觸者健康監測檢驗確診；51%麻疹確定病例經流行病學調查確認具有接觸史，發生場域包含醫療院所(23%)、國際機場及航空器(11%)等處。有近6成急性期血清抗體檢驗為IgM(-)/IgG(+)，疑因疫苗保護力下降(waning immunity)產生之突破性感染，雖症狀較不典型，但仍有部分突破性感染者造成次波疫情發生。未接種疫苗幼兒感染後臨床表現接近原發性感染(primary infection)之典型症狀，為疫情高峰期間不明感染源比例較多之年齡層。 討論：臺灣為高麻疹疫苗接種率及低發生率國家，感染主因為年輕成人疫苗保護力下降產生之突破性感染、境外移入相關因素與接觸史。突破性感染者不易由臨床症狀進行鑑別診斷，建議醫護人員可透過了解患者病程及接觸史，同時進行麻疹分子生物及抗體檢驗，以及早診斷避免疫情傳播。另就日後臺灣成人MMR疫苗接種政策，可進一步評估是否針對不同疫苗接種政策受惠世代提出不同接種建議，如本研究發現1976年以後出生之年輕成人(以1981年以後出生者尤其重要)，在出國前或國內發生本土麻疹疫情時，可建議補種1劑MMR疫苗，以增加群體免疫力。另外針對高風險職業，如醫療院所或國際機場工作者，亦可評估職前接種MMR疫苗，減少職業暴露風險。

Background: Measles has surged in 2018–2019, with large measles outbreaks around the world. Taiwan was also affected by the global outbreak. The confirmed cases exceeded the previous annual records. The study amid to explore the incidence rate for implementation of the prevention policy, and to further find out the risk factors or clinical characteristics of measles. Methods: We conducted a retrospective cohort study that enrolled the confirmed measles cases from 2002-2019 in national web-based Notifiable Diseases Surveillance System. Based on the national immunization program, the study were classified 3 cohort: Cohort A (born before Sep. 1976, pre-mass vaccination), Cohort B (born in Sep. 1976–Sep. 1990, 2 dose of MV and 1 dose of MMR) and Cohort C (born after Sep. 1990, at least 2 dose of MMR). We analyzed category variables such as demographic factor, clinical characteristics, vaccination history, contact history and travel history. The chi-squared test and fisher exact test were used to identify variables associated with different cohort. Results: There were 397 confirmed cases from 2002 through 2019, of which 44.8% where Cohort B and 18-38 years of age. In addition, we analyzed the clinical presentation of 168 confirmed cases from 2018 through 2019, fever (89%) and rash (95%) were the most common symptoms, and 49% didn't have the symptoms of cough, coryza, and conjunctivitis. According to epidemiological investigation, 83% were imported or importation-related cases, 51% had a record of a contact history, 23% cases occurred in healthcare-settings and 11% in international airport or airplane settings. Nearly 60% cases of the acute-phase serum antibody test was IgM(-)/IgG(+), suspected of breakthrough infection caused by reduced vaccine protection (waning immunity). Conclusion: Taiwan is a country with stronger measles historical vaccination programs and low incidence rate. The onset age shift to young adult, breakthrough infections were common. The findings of this study could improve the clinical diagnosis and decision making of vaccination programs.