You might believe you're immune,

你可能會認為你是免疫的。

in the clear to go about your normal life

逍遙自在

without safety precautions.

沒有安全防範措施。

But with scattered reports of recovered cases

但是，隨著零星的關於追回案件的報告。

testing positive again,

再次測試陽性。

a lot of people are wondering if it's possible

很多人都想知道是否有可能

to develop immunity at all.

形成免疫力的根本。

So, can you catch COVID-19 twice?

那麼，你能趕上COVID-19兩次嗎？

The thing is, scientists just aren't sure,

問題是，科學家們只是不確定。

because figuring that out

因為搞清楚了

is a lot more complicated than you might think.

比你想象的要複雜得多。

When a pathogen like a virus

當病毒等病原體

manages to get into a human,

管理進入人類。

their body will signal an alarm.

他們的身體會發出警報信號。

This will start what's referred to

這將啟動所謂的

as the innate immune response

作為先天性免疫反應

and consists of physical, chemical,

並由物理、化學。

and cellular defenses against pathogens.

和細胞對病原體的防禦能力。

Often enough, this works, and the invader is killed,

通常情況下，這招很管用，入侵者就會被殺死。

but sometimes you need a second attack.

但有時你需要第二次攻擊。

The adaptive immune response marshals

適應性免疫反應集合了

the special forces:

特種部隊。

B cells and T cells.

B細胞和T細胞。

B cells produce antibodies

B細胞產生抗體

that smother the specific pathogen

窒息特定病原體

so it can't affect your body's cells.

所以不能影響你身體的細胞。

Shane Crotty: So, basically, antibodies

Shane Crotty：所以，基本上，抗體。

kill virus outside of cells;

殺死細胞外的病毒。

killer T cells kill virus inside of cells.

殺手T細胞殺死細胞內的病毒。

Narrator: So, once your body fights the pathogen,

所以，一旦你的身體對抗了病原體，所以，一旦你的身體對抗病原體，

what stops you from having to fight off

是什麼阻止了你不得不打掉

the same attack over and over?

同樣的攻擊一次又一次？

Well, your body has a secret weapon

嗯，你的身體有一個祕密武器

to protect you against any future attacks

以保護您免受任何未來的攻擊

from the same pathogen: memory cells.

來自同一病原體：記憶細胞。

Memory cells are

記憶細胞是

basically the specialized

基本上是專門

T cells and B cells that stick around as guards.

T細胞和B細胞，作為守衛堅持下來。

That way, if you encounter the virus again,

這樣一來，如果你再遇到病毒。

the army will be readily waiting

兵來將擋，水來土掩

to kill that invader instantly.

來瞬間殺死那個入侵者。

This is immunity.

這就是免疫力。

A vaccine works on this basis by adding dead,

疫苗在此基礎上通過添加死。

weakened, or fragmented parts

殘缺不全

of a pathogen to your body.

的病原體對你的身體。

Not enough to cause illness,

不足以致病。

but enough to cause

但足以引起

your body to produce memory cells.

你的身體產生記憶細胞。

Crotty: Normally, when you have an infection,

克羅蒂：通常情況下，當你有感染。

it's a race between your immune system

這是你的免疫系統之間的比賽。

and the infection.

和感染。

But if you're vaccinated,

但如果你接種了疫苗。

you've already done the race part.

你已經做了比賽的一部分。

Your immune system has already had time

你的免疫系統已經有時間

to scale up and develop immunity.

以擴大規模，發展免疫力。

Narrator: Typically, you would know

旁白：一般來說，你會知道

if you have immunity,

如果你有免疫力。

either from a vaccine

無論是從疫苗

or knowing you previously had the illness.

或知道自己以前得過這種病。

For example, it's relatively straightforward to know

例如，比較直接的是，要知道

whether you've had chickenpox or not

是否出過水痘

because the symptoms are highly unique

因為症狀非常獨特

and very easy to spot.

並且非常容易發現。

But let's presume you know you've had COVID-19.

但我們假設你知道你有COVID -19。

You now have immunity and are safe, right?

你現在有了免疫力，安全了吧？

To test this theory, one early study

為了檢驗這一理論，一項早期的研究

infected monkeys with the COVID-19 virus.

用COVID-19病毒感染猴子。

They then waited till they tested negative

然後等到他們的檢測結果呈陰性

after the infection passed and tried to reinfect them.

感染過去後，試圖重新感染他們。

When the monkeys didn't become reinfected,

當猴子沒有成為再感染。

researchers concluded that after one viral attack,

研究人員認為，在一次病毒攻擊後。

you would be protected from another.

你會受到另一個人的保護。

But this isn't a golden ticket to thinking you're immune,

但這並不是一張自以為免疫的金票。

because the length and strength

因為長度和強度

of that potential immunity are unknown.

這種潛在的免疫力是未知的。

And where a disease lies on the spectrum

而一種疾病位於光譜上

is influenced by two things,

是受兩個方面的影響。

memory cell death rate and virus mutation rate.

記憶細胞死亡率和病毒變異率。

Memory cell death rate tells you at what rate

記憶細胞死亡率告訴你以什麼速度

those memory cells may be lost over time.

這些記憶細胞可能會隨著時間的推移而丟失。

The virus mutation rate can tell you if the virus

病毒的突變率可以告訴你，病毒是否有

will mutate too quickly for your memory cells.

會讓你的記憶細胞突變得太快。

The more a virus mutates, the more unrecognizable

病毒越是變異，越是無法識別

it becomes to your memory cells.

它變成了你的記憶細胞。

Determining where COVID-19

確定COVID-19的位置

falls on this timescale

屬於這個時間段

is a vital step in managing its spread.

是控制其蔓延的重要步驟。

One indication of how long its immunity might last

說明其免疫力可能持續多久的一個標誌。

is to look at other coronaviruses.

是看其他冠狀病毒。

Those who have contracted SARS-1

感染SARS-1的人

have been found to have immunity

已被發現具有免疫力

for about two to three years,

約兩到三年的時間。

and the same time frame has been seen

而同樣的時間段也出現了

in other coronaviruses that can cause the common cold.

在其他可引起普通感冒的冠狀病毒中。

Yet early signs have shown

然而，早期跡象表明

that this virus tends to mutate slowly.

這種病毒往往變異緩慢。

But there's another indicator

但還有一個指標

into immunity strength and length:

成免疫力強度和長度。

the serology test.

血清學檢測。

Crotty: The serology testing is a blood test

Crotty：血清學檢測是一種血液檢測。

for the presence of antibodies against

對抗抗體的存在

that specific virus or that specific disease.

該特定病毒或特定疾病。

Narrator: Importantly, these are tests that can be done

旁白：重要的是，這些都是可以做的測試。

after you've recovered from symptoms.

在你從症狀中恢復後。

Crotty: And you don't have to know exactly

Crotty:你不必知道究竟

when that person was infected.

當該人被感染時。

And so that's a very powerful way to count

所以，這是一個非常強大的方式來計算。

how many people have actually been infected,

究竟有多少人被感染了。

whether they recognize the symptoms or not.

無論他們是否認識到這些症狀。

Narrator: These tests can measure

旁白：這些測試可以測量

how many antibodies are in the sample

樣品中含有多少抗體

by looking at how they block or respond to the virus.

通過研究它們如何阻止或應對病毒。

These measurements can help to understand

這些測量可以幫助瞭解

immunity levels and how long immunity could last.

免疫力水準和免疫力可以持續多久。

For example, studies for many other viral infections

例如，對許多其他病毒感染的研究。

have found that

發現

the more severe the case,

情況越嚴重。

the longer the immunity.

免疫力越強。

Basically, the bigger the infection,

基本上，感染越大。

the bigger the immune response

免疫反應越大

and more antibodies in a sample,

和樣品中更多的抗體。

which in turn gives longer immunity.

從而獲得更長的免疫力。

But this may not hold true for COVID-19.

但對於COVID-19來說，情況可能不盡然。

Crotty: It certainly may not be as simple as

克羅蒂：當然可能沒有那麼簡單。

if you're positive for the antibody,

如果你的抗體呈陽性。

you're protected against the disease, you're immune.

你對疾病的保護，你的免疫力。

That's true for many infections;

很多感染都是如此。

it's not proven for COVID-19 disease.

它對COVID-19疾病沒有證明。

Narrator: And the effectiveness of certain

旁白：而某些東西的有效性

serology tests for COVID-19 has been mixed.

COVID-19的血清學測試結果喜憂參半。

Some tests are being misused,

一些測試被濫用。

and others were brought into the United States

和其他人被帶入美國

before the FDA could approve them.

在FDA準許之前，他們。

The result has been poor detection rates,

其結果是檢測率不高。

some as low as 20%.

有的低至20%。

Crotty: You know, these are the same types of tests

克羅蒂：你知道，這些都是相同類型的測試。

as a pregnancy test.

作為懷孕測試。

And so there's no way people would take pregnancy tests

所以人們不可能去做妊娠測試

if they were only accurate 60% of the time.

如果他們只有60%的準確率。

Narrator: And there have been instances

旁白：也有過這樣的情況

of false positives, which can be extremely dangerous,

的假陽性，這可能是極其危險的。

because they arm people with

因為他們把人們武裝在

a false sense of potential immunity.

潛在的免疫力的錯誤意識。

But these problems aren't universal,

但這些問題並不普遍。

and the FDA has begun approving a select few

和FDA已經開始準許一些選定的少數幾個。

that show much higher accuracy.

顯示出更高的準確性。

So, with an accurate serology test,

所以，在準確的血清學檢測下。

would you be immune?

你會有免疫力嗎？

Well, one early Chinese study

那麼，中國早期的一項研究

found 30% of those who tested positive for the virus

發現30%的病毒檢測呈陽性。

had little to no detectable antibodies,

幾乎沒有檢測到抗體。

which would suggest that immunity isn't guaranteed,

這說明免疫力並沒有保證。

though this has been challenged by another study

儘管這一點受到另一項研究的質疑

that found all patients tested

發現所有的患者都接受了測試

had significant antibody levels.

有顯著的抗體水準。

But other issues such as age or health

但其他問題，如年齡或健康

could play into these responses.

可能會對這些反應產生影響。

Crotty: Is it gonna be 0.1% of people

克羅蒂：會是0.1%的人嗎？

who can get reinfected three months later?

誰能在三個月後再感染？

Or is it going to be a higher number in the elderly?

還是在老年人中會比較多？

Narrator: Once more accurate and universal

旁白：再準確、再普遍

testing is underway,

正在進行測試。

more studies can begin to more precisely examine

更多的研究可以開始更精確地檢查

how long this immunity may last and who has it.

這種免疫力可能持續多久，誰擁有這種免疫力。

So our best bet right now is to keep our distance

所以我們現在最好的辦法就是保持距離。

and assume we're not immune at all.

並認為我們根本沒有免疫力。