新冠肺炎病毒之群體免疫、疫苗研發與卡介苗功效

Herd Immunity, Vaccine Development and BCG Effects in COVID-19

柯獻欽(Shian-Chin Ko) ； 鄭高珍(Kuo-Chen Cheng) ； 莊銀清(Yin-Ching Chuang)

《內科學誌》 31卷4期 (2020/08) Pp. 254-261

https://doi.org/10.6314/JIMT.202008_31(4).05

摘要

新冠肺炎（COVID-19）自2019年底由中國武漢開始，已蔓延到全世界，迄今（2020年6月30日）在全球造成1,030萬人感染，高達50.4萬人喪生，堪稱本世紀最大的瘟疫，在人類健康與社會經濟上造成巨大損害。新型冠狀病毒（SARS-CoV-19）的下一步，大部分的專家認為可能會流感化而與人類共存，所以根本的解決方法，除了依靠自身的免疫力之外，就是要依靠疫苗。群眾在感染之後的自然免疫，形成一道保護牆，阻礙病毒在人群中傳播，保護著沒有免疫力的個體，此之謂群體免疫（herd immunity），然而前提是有抗體的人數要夠多，才不會產生破口，但目前尚無任何國家達到此條件。長期而言，疫苗才是完勝新興傳染病的解方，因此各國無不加緊腳步，如火如荼地投入疫苗研發的工作，然而因時間緊迫而縮短疫苗研發時程，可能使疫苗的安全性與有效性出狀況，以至於增加失敗風險，故仍應按部就班，不能省略必要的研發步驟。既然新疫苗緩不濟急，因觀察到常規施打卡介苗的國家，其COVID-19的罹病與死亡人數顯著較低，老藥新用的卡介苗再定位就被提出來討論，然而目前並無直接證據顯示卡介苗可預防或減輕COVID-19，仍有待進一步臨床研究證實，現階段並不建議施打卡介苗來預防COVID-19。

關鍵字

新冠肺炎病毒（Severe acute respiratory syndrome coronavirus 2, SARS-CoV-2） ； 群體免疫（Herd immunity） ； 疫苗（Vaccine） ； 卡介苗（Bacille Calmette-Guérin, BCG）

並列摘要

COVID-19 has spread to the world since the end of 2019 in Wuhan, China. It has caused more than ten million infections worldwide and killed more than 500,000 people. It is the largest plague in this century and causes huge damages in human health and social ecology. In the next step, many experts believe that COVID-19 may become flu-like and coexist with humans. The fundamental solutions of COVID-19, in addition to our own immunity, are to rely on vaccination. The natural immunity of the people after infection has formed a protective wall that protects the naïve individuals and prevents disease spreading among the population. This is called herd immunity. But the prerequisite is that there must be enough people with antibodies. Unfortunately, no country meets the requirements till now. In the long run, vaccines are the final solution for newly developed infectious diseases. Owing to time constraints, all countries have stepped up their efforts to invest in vaccine research and development in full swing. However, testing vaccines and medicines without taking the time to fully understand safety risks could bring unwarranted setbacks during the current pandemic, and into the future. We should not omit the necessary R&D steps. Since the new vaccine is not in a hurry and we observe that the number of illnesses and deaths of COVID-19 is significantly lower in countries with conventional BCG vaccine schedule, the use of BCG vaccines is proposed for discussion. But there is no direct evidence at present showing BCG vaccine can prevent COVID-19 or reduce its severity. To be confirmed by further clinical studies, at this stage, it is not recommended to use BCG vaccine to prevent COVID-19.