How do vaccines work? - Kelwalin Dhanasarnsombut

疫苗的工作原理 - Kelwalin Dhanasarnsombut

翻译人员: Peipei Xiang 校对人员: Emily(Hongyu) Chen

1796年，科学家爱德华·詹纳

In 1796, the scientist Edward Jenner

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

把牛痘病毒 注入到了一个八岁男孩的体内，

with a hunch that this would provide the protection needed

他直觉这可以保护人们

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

免受天花病毒爆发的致命威胁。

It was a success.

他成功了！

The eight-year-old was inoculated against the disease

这个八岁男孩没有感染天花，

and this became the first ever vaccine.

这成了历史上的第一支疫苗。

But why did it work?

但是它是怎么发挥作用的呢？

To understand how vaccines function,

要了解疫苗的作用原理，

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

我们必须先了解我们的免疫系统是

如何帮助我们打败传染病的。

in the first place.

When foreign microbes invade us,

当外界微生物入侵我们的身体时，

the immune system triggers a series of responses

免疫系统会做出一系列反应

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

试图识别并将异物赶出去。

The signs that this immune response is working

免疫系统正常的表现包括

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

咳嗽、打喷嚏、发炎、发烧等等，

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

这些都是为了把体内的威胁物，如细菌， 困住、吓跑。

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

这些先天的免疫反应 还会诱发我们的第二道防线，

called adaptive immunity.

叫做适应性免疫。

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

特殊的细胞，B细胞和T细胞 会被召集起来对抗微生物

and also record information about them,

并记录有关它们的信息，

creating a memory of what the invaders look like,

记录下这些入侵者的样子

and how best to fight them.

以及如何最有效地打败他们。

This know-how becomes handy

这些信息在同样的病原体 再次入侵的时候就非常有用。

if the same pathogen invades the body again.

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

不过尽管如此，这还是有风险的。

The body takes time to learn how to respond to pathogens

身体需要一定的时间才能学会 如何对一病原体做出反应

and to build up these defenses.

并建立相应的防御。

And even then,

即便如此，

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

如果一个人的身体太虚弱或太年轻， 在身体被入侵的时候不能反抗，

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

这个人可能会有很严重的生命威胁， 特别是如果这个病原体很厉害的话。

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

但是，如果我们可以提前 给我们的身体免疫系统做好准备，

readying it before someone even got ill?

甚至在我们生病以前就准备好呢？

This is where vaccines come in.

这里就是疫苗发挥作用的地方了。

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

运用跟身体自身防御一样的原理，

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

科学家们用疫苗诱发身体的 适应性免疫系统，

without exposing humans to the full strength disease.

但人们不需要遭受疾病之苦。

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

现在我们已经有了很多疫苗， 每种疫苗都有各自独特的工作原理，

separated into many different types.

可以分成许多不同的种类。

First, we have live attenuated vaccines.

首先，我们有减毒疫苗，

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

它们由病原体本身制成， 但是是比较弱的病原体。

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

接着，我们有失活疫苗， 这些疫苗中的病原体已经失去活性。

The weakening and inactivation in both types of vaccine

这两种疫苗的弱化和失活

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

保证病原体没有机会完全发病。

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

但是就跟疾病一样， 它们会诱发免疫系统反应，

teaching the body to recognize an attack

让身体识别来自外部的袭击，

by making a profile of pathogens in preparation.

这都是通过提前建立病原体档案做到的。

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

不过，减毒疫苗的缺点是它很难生产，

and because they're live and quite powerful,

因为它们是活的而且很强大，

people with weaker immune systems can't have them,

那些免疫系统较弱的人不能够接种它们；

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

而失活疫苗则不能产生长期的免疫性。

Another type, the subunit vaccine,

另一种是亚单位疫苗，

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

它是由病原体的一个部分制成，即抗原，

the ingredient that actually triggers the immune response.

抗原是诱发免疫系统反应的部分。

By even further isolating specific components of antigens,

通过进一步分离抗原的具体成分，

like proteins or polysaccharides,

比如蛋白质或多糖，

these vaccines can prompt specific responses.

这些疫苗可以诱发相应的反应。

Scientists are now building a whole new range of vaccines

科学家们现在正在打造一系列的DNA疫苗。

called DNA vaccines.

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

这种疫苗是将组成某种抗原的身体需要的

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

用来诱发免疫系统反应的 特定基因分离出来。

When injected into the human body,

当这种疫苗被注入体内的时候，

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

这些基因会告知体内的细胞制造抗原，

This causes a stronger immune response,

这可以产生更强的免疫反应，

and prepares the body for any future threats,

为以后任何可能的威胁做好准备。

and because the vaccine only includes specific genetic material,

并且因为这种疫苗 只包含了特定的基因成分，

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

它不包含任何其他来自病原体的

that could develop into the disease and harm the patient.

可能会导致病人发病而受苦的成分。

If these vaccines become a success,

如果这些疫苗获得成功，

we might be able to build more effective treatments

我们也许能够在不久的将来打造 更加有效的针对强大病原体的治疗方案。

for invasive pathogens in years to come.

Just like Edward Jenner's amazing discovery

就跟爱德华·詹纳的伟大发现

spurred on modern medicine all those decades ago,

推动了现代医学的发展一样，

continuing the development of vaccines

继续致力于疫苗的研究

might even allow us to treat diseases like HIV,

也许有一天会让我们能够治疗艾滋病、

malaria,

疟疾、埃博拉等。

or Ebola, one day.