How do vaccines work? - Kelwalin Dhanasarnsombut

疫苗的原理為何？─ 柯娃玲 (Kelwalin Dhanasarnsombut)

譯者: Chingwen Kao 審譯者: Regina Chu

In 1796, the scientist Edward Jenner

1796 年，科學家愛德華·簡納

injected material from a cowpox virus into an eight-year-old boy

將牛痘病毒中的物質 注射到八歲男童身上

with a hunch that this would provide the protection needed

並有預感此舉將能為致命的天花疫情

to save people from deadly outbreaks of the related smallpox virus.

提供預防方法 拯救民眾生命

It was a success.

此法相當成功

The eight-year-old was inoculated against the disease

這名接受接種的八歲男童能抵禦天花

and this became the first ever vaccine.

世界首個疫苗於焉問世

But why did it work?

但這背後的原理為何？

To understand how vaccines function,

想知道疫苗原理

we need to know how the immune system defends us against contagious diseases

就得先了解人體免疫系統 是如何在第一時間

in the first place.

抵抗傳染疾病

When foreign microbes invade us,

當遭受外來病菌侵襲時

the immune system triggers a series of responses

免疫系統會啟動一系列反應

in an attempt to identify and remove them from our bodies.

試圖辨識並將這些病菌趕出體外

The signs that this immune response is working

免疫反應的徵兆包括

are the coughing, sneezing, inflammation and fever we experience,

我們經歷到的咳嗽 打噴嚏、發炎及發燒

which work to trap, deter and rid the body of threatening things, like bacteria.

這都是為了將危害物質如細菌等 包圍、遏止並趕出體外

These innate immune responses also trigger our second line of defense,

此先天免疫反應也會誘發第二道防線

called adaptive immunity.

稱之為後天性免疫

Special cells called B cells and T cells are recruited to fight microbes,

特殊的 B 細胞及 T 細胞 會被徵招來抵抗病菌

and also record information about them,

並記錄下病原菌資訊

creating a memory of what the invaders look like,

以存檔了解侵略者的外觀

and how best to fight them.

及最佳抵禦方式

This know-how becomes handy

下次再碰上同樣病原體時

if the same pathogen invades the body again.

這些實戰知識就能立即拿來使用

But despite this smart response, there's still a risk involved.

但儘管免疫反應如此精巧 還是有風險存在

The body takes time to learn how to respond to pathogens

因為身體需要花時間 才能了解如何因應病菌

and to build up these defenses.

及建立防禦措施

And even then,

即便如此

if a body is too weak or young to fight back when it's invaded,

若在發育未臻成熟或體衰時得病 就無法有效抵抗疾病

it might face very serious risk if the pathogen is particularly severe.

因此若碰上特別棘手的病菌時 就可能面臨非常嚴重的危險

But what if we could prepare the body's immune response,

但要是能在第一次得病前

readying it before someone even got ill?

就讓免疫系統做好對抗疾病的準備呢？

This is where vaccines come in.

這就是疫苗的由來

Using the same principles that the body uses to defend itself,

原理就跟身體的自我防禦一樣

scientists use vaccines to trigger the body's adaptive immune system,

科學家利用疫苗來誘發 身體的後天免疫系統

without exposing humans to the full strength disease.

但免除讓人體暴露於完整病程中

This has resulted in many vaccines, which each work uniquely,

於是許多疫苗問世 這些疫苗可被分成多種類別

separated into many different types.

每個都有其獨特的作用方式

First, we have live attenuated vaccines.

首先 有活性減毒疫苗

These are made of the pathogen itself but a much weaker and tamer version.

由已被削減致病性的活體病菌所製成

Next, we have inactive vaccines, in which the pathogens have been killed.

另外還有非活性疫苗 此疫苗中的病原菌已全被殺死

The weakening and inactivation in both types of vaccine

此兩種疫苗中含有 已被弱化或無活性病菌

ensures that pathogens don't develop into the full blown disease.

可確保該病原菌 不會在人體內發展成真正的疾病

But just like a disease, they trigger an immune response,

但卻又能像疾病一樣 誘發免疫反應

teaching the body to recognize an attack

為目標病菌建立檔案

by making a profile of pathogens in preparation.

教導身體辨識該病菌的侵襲

The downside is that live attenuated vaccines can be difficult to make,

活性減毒疫苗的缺點是難以製備

and because they're live and quite powerful,

且因內含活性相當強大的病菌

people with weaker immune systems can't have them,

免疫系統弱的人並不適合接受接種

while inactive vaccines don't create long-lasting immunity.

而非活性疫苗的缺點則是 無法產生長久的免疫效力

Another type, the subunit vaccine,

另一種疫苗類型： 次單位疫苗

is only made from one part of the pathogen, called an antigen,

這種疫苗只含部分病原體 稱之為抗原

the ingredient that actually triggers the immune response.

也是真正誘發免疫反應的成分

By even further isolating specific components of antigens,

而進一步分離出抗原中的特定成分

like proteins or polysaccharides,

如蛋白質或多醣

these vaccines can prompt specific responses.

這類型疫苗可立即促使特定反應

Scientists are now building a whole new range of vaccines

科學家現已著手建立新的疫苗系列

called DNA vaccines.

稱之為 DNA 疫苗

For this variety, they isolate the very genes that make the specific antigens

為使身體對特定病菌產生免疫反應

the body needs to trigger its immune response to specific pathogens.

他們分離出目標抗原的基因

When injected into the human body,

而人體在接受注射後

those genes instruct cells in the body to make the antigens.

疫苗內的基因 會指示體內細胞製造抗原

This causes a stronger immune response,

這會引發更強大的免疫反應

and prepares the body for any future threats,

讓身體準備好對抗任何潛在威脅

and because the vaccine only includes specific genetic material,

此類型疫苗僅由特定基因物質組成

it doesn't contain any other ingredients from the rest of the pathogen

因此不含病原菌其它可能

that could develop into the disease and harm the patient.

致病並危害病人健康的物質

If these vaccines become a success,

若能研發成功

we might be able to build more effective treatments

就可能在幾年內 建立更有效的治療方法

for invasive pathogens in years to come.

來對抗侵入性病菌的感染

Just like Edward Jenner's amazing discovery

正如簡納當年的驚人發現

spurred on modern medicine all those decades ago,

促成過去數十年的醫學進步

continuing the development of vaccines

隨著疫苗技術的持續發展

might even allow us to treat diseases like HIV,

也許有天也能找到治療愛滋病

malaria,

瘧疾

or Ebola, one day.

或伊波拉的方法