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为什么流感疫苗需要每年接种一次?

Why do you need to get a flu shot every year? - Melvin Sanicas

“疫苗拯救生命 恐惧危及生命”- 杰弗里•克鲁格 时代周刊高级编辑
“Vaccines save lives; fear endangers them.” – Jeffrey Kluger, Senior Editor, TIME Magazine
世界各地的数百家医院的研究人员整年
All year long, researchers at hundreds of hospitals around the world
从流感患者身上采集样本
collect samples from flu patients
并将它们送给顶级病毒学专家 只为一个目的:
and send them to top virology experts with one goal:
研究下一个流感季节的疫苗
to design the vaccine for the next flu season.
但是为什么我们每年都要新的疫苗呢?
But why do we need a new one every year?
腮腺炎 风疹的疫苗只要小时候注射两次
Vaccines for diseases like mumps and rubella offer a lifetime of protection
人就能得到终身防护
with two shots early in life.
那流感特殊在哪?
What’s so special about the flu?
两个因素让流感应对比较棘手
Two factors make the flu a tough target.
第一 流感病毒存在上百种的亚型
First,there are more than 100 subtypesof the influenza virus,
在不同的季节里 流行病的病毒都不同
and the ones in circulationchange from season to season.
第二 流感病毒的遗传密码
And second, the flu’s
使它比其他病毒变异速度更快
genetic code allows it to mutate more quickly than many other viruses.
流感病毒通过把宿主细胞变成其生产工厂而得以传播
The flu spreads by turning a host’s own cells into viral production factories.
当病毒被宿主细胞吞噬
When the virus is engulfed by a host cell,
病毒的遗传物质就会被释放
it expels its genetic material,
到达细胞核
which makes its way to the nucleus. There,
细胞核通常是宿主细胞基因复制的地方
cellular machinery that normallycopies the host’s genes
这时就会开始复制病毒的基因
starts replicating viral genes instead,
生成源源不断的病毒副本
creating more and more copiesof the virus.
新的病毒会被重新装配
New viruses are repackaged and crammed
细胞内产生更多的病毒直到它破裂
into the cell until it bursts,
再次将新装配好的流感病毒传播 感染更多的细胞
sending freshly minted influenza virusesout to infect additional cells.
大部分病毒都是遵循这个流程
Most viruses follow this script.
流感病毒的狡猾之处在于
The trick with the flu is
它的遗传物质不是DNA
that its genetic material isn’t DNA
而是一个和DNA相似的结构 叫RNA
but a similar compound called RNA.
RNA病毒变异的速度更快
And RNA viruses can mutate much faster.
当细胞合成DNA时 有一个内在的机制检查并纠正错误
When cells synthesize DNA, a built-in proofreader recognizes and corrects mistakes,
但是RNA 合成机制没有纠错机制
but the RNA synthesis mechanismdoesn’t have this fail-safe.
如果错得很多 就会创造一个新的病毒变种
If errors creep in, they stick around creating new variants of the virus.
为什么这是个问题呢?
Why is this a problem?
因为疫苗是依赖识别机制的
Because vaccines depend on recognition.
流感疫苗里有一些叫做抗原的物质
The flu vaccine includes some of the samesubstances, called antigens,
在流感病毒表面也有
found on the surface of the virus itself.
身体将这些片段识别为外来物
The body identifies those fragmentsas foreign
然后生成与抗原相匹配的抗体来应对
and responds by producing compoundscalled antibodies,tailor-made to match the antigens.
接种疫苗的人遇到病毒后
When a vaccinated personencounters the actual virus,
预先编排好的抗体会帮助免疫系统识别威胁
the preprogrammed antibodieshelp the immune system identify the threat
然后快速动员机体来防止感染
and mobilize quicklyto prevent an infection.
每一株流感的抗原都是不同的
Those antigens are differentfor every strain of influenza.
如果疫苗接种只准备一个菌株的免疫系统
If vaccination has preparedthe immune system for one strain,
不同的病毒可能仍可能漏网
a different one may stillbe able to sneak by.
即使是同一种流感病毒
Even within the same strain of flu,
由于基因快速变异 病毒表面化学物发生改编
those rapid genetic mutations can change the surface compounds enough
抗体仍有可能无法识别病毒
that the antibodiesmay not recognize them.
让问题更加复杂的是
To make things even more complicated,
有些时候两种不同的病毒毒株会联合产生一种完全不同的杂交病毒
sometimes two different strains combine to create an entirely new hybrid virus.
这些因素导致流感疫苗就好像是
All of this makes vaccinating for the flu
在尝试击中一个既会移动又会变形的靶子
like trying to hit a movingtransforming target.
所以 科学家们不断地收集数据
That’s why scientists are constantlycollecting data
弄清哪些毒株正在流行
about which strains are circulating
并检查这些毒株相比几年前
and checking to see how much those strains have mutated
发生了多少变异
from previous years’ versions.
世界卫生组织每年两次召集专家
Twice annually, the WorldHealth Organization pulls together experts
去分析所有的数据 为南北半球各召开会议
to analyze all that data, holding one meeting for each hemisphere.
科学家决定这一流行季中流感病毒毒株类型
The scientists determine which strains to include in that season’s vaccine,
选择四中毒株 制作四价疫苗
picking four for the quadrivalent vaccine in use today.
尽管流感病毒有逃避策略
In spite of the flu’s evasive maneuvers,
在这几年来 该组织的预测几乎是全部正确的
in recent years, the group’s predictions have been almost always correct.
甚至当流感毒株进一步变异
Even when flu strains mutate further,
疫苗也不会相差太远
the vaccine is often close enough
接种疫苗的人 相比未接种的人
that a vaccinated person who catches the flu anyway
在感冒后病情更轻 病程更短
will have a milder and shorter illnessthan they would otherwise.
接种疫苗后 通过防止其携带病毒
Vaccination also helps protectother people in the community
能有助于保护社区内不宜接种疫苗的人
who may not be medically eligiblefor the shot
免于感染
by preventing those around themfrom carrying the virus.
这叫做群体免疫
This is called herd immunity.
接种流感疫苗不会使人患上流感
The flu shot can’t give you the flu.
因为它含有的是灭活病毒 它不会使人患病
It contains an inactivated virus that isn’t capable of making you sick.
注射疫苗后 有可能会感到疲倦和酸痛
You might feel tiredand achy after getting it,
但那不是感染
but that’s not an infection.
这只是对疫苗的正常免疫反应
It’s your normal immune responseto the vaccine.
世界上还有一些地方
Some parts of the world use,
使用的疫苗不是注射式 而是吸入室
instead of a shot, an inhaled vaccine
吸入式疫苗含有弱化活病毒
that contains a weakened live virus.
对于大部分人来说也是安全的
This is also safe forthe vast majority of people.
只有对免疫系统受损或缺陷的人才有危险
Only those with impaired immune systems would be at risk,
但这些人通常是不会接种活疫苗的
but they’re typicallynot given live vaccines. Meanwhile,
同时 科学家正试图研发万能的流感疫苗
scientists are workingto develop a universal flu vaccine
这可以预防所有的毒株 甚至是变种
that would protect against any strain,even mutated ones.
不过在那之前 下一年的疫苗搜寻研究工作还在继续
But until then, the huntfor next year’s vaccine is on.
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视频详细说明了为什么每天都需要接种疫苗

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收集自网络

翻译译者

杜小雅

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审核员 LD

视频来源

https://www.youtube.com/watch?v=FZ_jNGKCIWs

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