How often should you get a flu shot? - Melvin Sanicas

譯者: Sherl H 審譯者: Sylvia He

All year long, researchers at hundreds of hospitals around the world

一年到頭 全世界數百間醫院的研究人員

collect samples from flu patients

從流感病人身上採集樣本

and send them to top virology experts with one goal:

並寄給頂尖的病毒學專家

目標就是為下一個流感季設計疫苗

to design the vaccine for the next flu season.

但為什麼我們每年都需要新的疫苗呢

But why do we need a new one every year?

Vaccines for diseases like mumps and rubella offer a lifetime of protection

像腮腺炎和德國麻疹這些疾病的疫苗

在幼兒期注射兩次就提供終生保護

with two shots early in life.

What's so special about the flu?

流感究竟有什麼特別的呢

Two factors make the flu a tough target.

有兩個因素使流感成為一個棘手的目標

First, there are more than 100 subtypes of the influenza virus,

首先 流感病毒有超過 100 種亞型

而且每季流行的亞型都不同

and the ones in circulation change from season to season.

And second, the flu's genetic code allows it to mutate more quickly

再來 流感的基因編碼

讓它比其他病毒更快突變

than many other viruses.

The flu spreads by turning a host's own cells into viral production factories.

流感的傳播是藉由 把宿主自身的細胞變成病毒製造工廠

When the virus is engulfed by a host cell, it expels its genetic material,

當病毒被宿主細胞吞噬 病毒會吐出它的遺傳物質

which makes its way to the nucleus.

遺傳物質然後進入細胞核

There, cellular machinery that normally copies the host's genes

在那裡 宿主細胞的基因複製的機制

starts replicating viral genes instead,

開始複製病毒的基因

creating more and more copies of the virus.

生產越來越多的病毒複本

New viruses are repackaged and crammed into the cell until it bursts,

新的病毒被重新包裝 直到細胞充滿病毒而炸開

sending freshly minted influenza viruses out to infect additional cells.

剛出爐的流感病毒 就被送去感染其他細胞

Most viruses follow this script.

多數病毒都依照這種模式傳播

The trick with the flu is that its genetic material isn't DNA

流感的詭計在於它的遺傳物不是 DNA

but a similar compound called RNA.

但卻是一種類似的化合物 稱為 RNA

And RNA viruses can mutate much faster.

RNA 病毒的突變速度快很多

When cells synthesize DNA,

當細胞合成 DNA

a built-in proofreader recognizes and corrects mistakes,

一種內建的校對酶會辨識並糾正錯誤

but the RNA synthesis mechanism doesn't have this fail-safe.

但 RNA 合成機制中 沒有這種自動防錯

If errors creep in, they stick around creating new variants of the virus.

如果錯誤悄悄出現 他們會被保存下來 導致新變種的病毒的產生

Why is this a problem?

這為什麼是個問題呢

Because vaccines depend on recognition.

因為疫苗依賴辨識

The flu vaccine includes some of the same substances, called antigens,

流感疫苗內含有某些 病毒表面存在的物質

found on the surface of the virus itself.

稱為抗原

The body identifies those fragments as foreign

身體辨識出哪些碎片是外來的

and responds by producing compounds called antibodies,

並製造稱為抗體的化學物質來因應

tailor-made to match the antigens.

抗體是量身打造的 不同的抗體配對不同的抗原

When a vaccinated person encounters the actual virus,

當打過疫苗的人遇到真正的病毒

the preprogrammed antibodies help the immune system identify the threat

身體裡針對疫苗產生的抗體 幫助免疫系統辨識危險

and mobilize quickly to prevent an infection.

並快速採取行動來預防感染

Those antigens are different for every strain of influenza.

每個品系的流感病毒都有不同的抗原

If vaccination has prepared the immune system for one strain,

如果疫苗讓免疫系統 為一種品系做好了準備

a different one may still be able to sneak by.

其他品系的病毒 或許還是可以瞞過免疫系統偷溜進來

Even within the same strain of flu,

即使是同一品系中的流感

those rapid genetic mutations can change the surface compounds enough

那些迅速的基因突變 可能使表面抗原改變的程度

that the antibodies may not recognize them.

大到讓抗體認不出來

To make things even more complicated,

讓情況更複雜的是

sometimes two different strains combine to create an entirely new hybrid virus.

有時兩種品系會結合 產生全新的混種病毒

All of this makes vaccinating for the flu

這一切都使製造流感疫苗

like trying to hit a moving transforming target.

變得像是在試圖打中一個 正在移動並變形的標靶

That's why scientists are constantly collecting data

這就是為什麼科學家持續地收集數據

about which strains are circulating

來研究哪些品系正在流行

and checking to see how much those strains have mutated

並檢查那些品系 與前幾年的版本相比

from previous years' versions.

突變的程度有多少

Twice annually, the World Health Organization pulls together experts

每年兩次 世界衛生組織招聚專家們

to analyze all that data,

來分析所有的數據

holding one meeting for each hemisphere.

在南北半球分別舉行一場會議

The scientists determine which strains to include in that season's vaccine,

科學家決定當季的疫苗需要包括哪些品系

picking four for the quadrivalent vaccine in use today.

選出四種製成現今使用的四價疫苗

In spite of the flu's evasive maneuvers,

即使流感有逃避的花招

in recent years, the group's predictions have been almost always correct.

這個團隊近年的預測幾乎總是正確的

Even when flu strains mutate further, the vaccine is often close enough

甚至當流感品系產生更多突變時 疫苗常是足夠接近和有效的

that a vaccinated person who catches the flu anyway

讓一個打過疫苗但仍得到流感的人

will have a milder and shorter illness than they would otherwise.

相對在未打疫苗的情況下 有較輕微並短暫的病情

Vaccination also helps protect other people in the community

疫苗也有助於保護社區中

who may not be medically eligible for the shot

其他在醫學上不具施打疫苗資格的人

by preventing those around them from carrying the virus.

籍由他們周圍的人打了疫苗 而降低了攜帶病毒的可能性

This is called herd immunity.

這叫做「群體免疫」

The flu shot can't give you the flu.

流感疫苗不會使你得流感

It contains an inactivated virus that isn't capable of making you sick.

它含有的失活病毒無法使你生病

You might feel tired and achy after getting it,

施打後你可能感到疲倦和虛弱

but that's not an infection.

但那不是感染

It's your normal immune response to the vaccine.

而是你對於疫苗的正常免疫反應

Some parts of the world use, instead of a shot, an inhaled vaccine

世界上有些地區不使用注射式

而使用吸入式 含有弱化活病毒的疫苗

that contains a weakened live virus.

This is also safe for the vast majority of people.

這對於大部分人也是安全的

Only those with impaired immune systems would be at risk,

只會威脅有那些免疫系統有缺失的人

but they're typically not given live vaccines.

但他們通常不會被給予活病毒疫苗

Meanwhile, scientists are working to develop a universal flu vaccine

與此同時 科學家 正努力研發一種萬能流感疫苗

that would protect against any strain, even mutated ones.

可以針對任何品系提供保護 甚至包括突變種

But until then, the hunt for next year's vaccine is on.

但在那之前 我們還是要 開始尋覓下一年的疫苗了