根據美國CDC記錄(Ref1),美國流感疫苗在2009-2019年之間的成效只有19-60%不等,並不理想。993Please respect copyright.PENANAOhXzEA3jMr
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箇中原因眾多,除了流感病毒經常變種得以戈能夠避開疫苗效果外,另一原因就是疫苗的保護效果非常之短。993Please respect copyright.PENANAWGbkwYXfOo
針對這一點,有科學家在《Science》發表文章,展示資料解釋為何流感疫苗的保護效果並不長久。993Please respect copyright.PENANAm6lnBBFU4J
Source: https://science.sciencemag.org/content/early/2020/08/12/science.aaz8432993Please respect copyright.PENANA6mm9VeRYsf
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我們的免疫系統細胞可大致分為T cell及B cell兩種,非常籠統來說,T cell有著殺死細胞的能力,而B cell則擁有製造抗體的功能;事實上,兩者有著眾多功用,為簡易起見不在這裡逐一詳述。993Please respect copyright.PENANAk74GLi02n9993Please respect copyright.PENANAqXq0nkIZ5H
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(圖2)以簡單方式將B cell分類的話,我們可以將它們分成兩種,Memory B cell及 Plasma cell,後者亦可稱為Bone marrow plasma cell。993Please respect copyright.PENANA5bkVSzE2a5
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Memory B cell有著繁殖生長的能力,但需要一定的時間才能製造抗體。相反,Plasma cell並沒有繁殖生長的能力,但換來的就是擁有無時無刻製造抗體的特質。993Please respect copyright.PENANAHdMqO7RFyh
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(圖3)993Please respect copyright.PENANAzBTjHYGPUN
流感入侵人體至誘發病徵所需的時間並不太長,很多時候Memory B cell並沒能及時製造抗體應對,換言之Plasma cell的存在便顯得非常重要。993Please respect copyright.PENANAKGxo1l4TGH
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奈何的是,科學家發現Plasma Cell的數量雖然在疫苗過後的28日有所上升,但一年之後數量便打回原形,變相接近沒有打過一樣。993Please respect copyright.PENANAj2LLfJJMwp
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有見及此,文章作者強烈建議日後的流感針應該配合Adjuvant(佐劑)打進體內,藉此增強身體對疫苗所產生的免疫反應,盼望藉此能夠加多強Plasma Cell的數量。993Please respect copyright.PENANAS3mtYJWu44
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只不過,有一部份人士認為Adjuvant(佐劑)有機會導致不理想的副作用,以最老舊款式的佐劑為例,接受疫苗者經常會出現傷口潰瘍的情況,因此佐劑這一回事亦漸漸被人棄用;993Please respect copyright.PENANAMoypFqQb6j
現時已有不少改良過的佐劑新設計,但仍有待證實及審核是否能安全地應用。993Please respect copyright.PENANAjOYooxLzaF
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總結來說,Plasma cell的最終數量,對疫苗帶來的保護效果及期效將起有巨大作用。
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Reference:993Please respect copyright.PENANAkvRyp8tD00
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Ref1: https://www.cdc.gov/flu/vaccines-work/effectiveness-studies.htm