Down with the flu
流感的克星–疫苗

Oct 16th 2009
From Economist.com

Two different viruses will lay millions low this winter
今年冬天，两种病毒将对数百万人的生命产生威胁。

IT HAS taken seven months for the vaccine intended to protect people from the potentially deadly H1N1 strain of influenza to start trickling onto pharmacy shelves. The first doses are now being made available in America. Supplies will remain limited for months to come. In the meantime, the vaccine—both the killed version that is injected and the attenuated live version that is given as a nasal spray—is being rationed to those reckoned most in need.

H1N1型流感有致命的危险。人们用七个月时间研制出了H1N1型流感疫苗，此疫苗将开始逐渐登上药房货架。美国第一支流感疫苗已经研制成功，但是在接下来的几个月疫苗的供给还会有些紧张。同时，灭活疫苗（注射接种）和减毒活疫苗（使用鼻用喷雾接种）将先提供给那些最需要疫苗的人群。

That means children, pregnant women, nursing staff and those who could easily infect other vulnerable groups—especially infants and people with weakened immune systems. Strangely, the new H1N1 strain of virus does not strike the elderly anything like as much as seasonal flu does. This relative immunity—the opposite of what normally happens each winter—suggests that they may have been exposed to something similar in the past.

这类人群包括：儿童、孕妇、护工以及易感染人群，特别是婴儿及抵抗力较弱的人。奇怪的是，这种新型H1N1流感病毒并不像季节性流感那样对老年人有什么伤害。这种相对的免疫力与往年冬天有所不同，这可能表明老年人已经同往年一样感染了流感病毒，从而对此种病毒产生了免疫力。

After camping out in the southern hemisphere during the northern hemisphere’s summer, the worrisome new virus—originally called “swine flu” when first reported in March in Mexico—has circled the globe and returned north with a vengeance. More than 375,000 cases have been reported to the World Health Organisation and 4,500 people have died in the current pandemic. The most recent influenza pandemic, of Hong Kong flu, swept the world in 1968-69 and killed 1m people. The last pandemic caused by an H1N1 strain was in 1918-20, when Spanish flu took an estimated 50m-100m lives.

这种新型病毒于三月份在墨西哥首次报导时，被称之为“猪流感”，现在已经在全球大范围蔓延，并且当病毒再次传播至北半球时，其危害程度比原来更为严重。世界卫生组织透露，全球已有大约375000人感染，其中4500人已经死亡。最近一次全球大规模流感是香港流感。香港流感于1968-69年席卷全球，导致一百万人死亡。上一次H1N1型流感爆发是在1918-20年，当时的西班牙流感夺去了大约五千万到一亿人的生命。

Part of the delay in delivering an H1N1 vaccine is a result of it not being just another seasonal flu. It is additional to, and entirely different from, the usual bout of influenza that kills upwards of 250,000 people around the world each winter. Manufacturers have still had to produce the usual “trivalent” vaccine for this year’s seasonal flu, plus a wholly different vaccine for the more deadly H1N1 strain. To protect themselves (and those around them) people should take both the seasonal flu vaccine and, when they can get it, a dose of the H1N1 vaccine as well.

H1N1疫苗投产的延迟也正说明这次流感有别于普通季节性流感。全球每年冬天爆发的季节性流感最多导致250000人死亡，而H1N1型流感却与这种流感完全不同。制药商仍然要生产治疗普通季节性流感的三价流感疫苗，如今又多了项任务，那就是生产对抗致死性H1N1型流感的疫苗。为了保护自己以及身边的人，如果有条件的话，人们应该在注射季节性流感疫苗的同时，同样注射一剂H1N1型流感疫苗。

The big question is, will they? A recent poll by Consumer Reports, a citizens’ advocacy publication, found that 43% of Americans were still undecided about getting vaccinated against H1N1. Your correspondent despairs at the half-truths and conspiracy theories that abound. One popular talk-show host even tweeted that folks who get vaccinated against the new H1N1 strain were idiots. So much for medical wisdom in 140 characters.

但问题是，人们为什么要注射。人们都喜爱的杂志–《消费者报告》近期的一项民意调查显示：有43%的美国人仍然没有决定是否要注射H1N1型流感疫苗。作为一名记者，我已经对这种大量存在的半真半假又或是充满阴谋的信息失望透顶。一位著名访谈节目主持人甚至说如果谁接种H1N1型流感疫苗谁就是傻瓜。

Urban myths about the dangers of influenza vaccines have lingered in America since the country’s panicked reaction to a swine-flu scare in 1976. A vaccine was rushed out and a quarter of the population hurriedly vaccinated before the programme was cancelled, after the successful containment of the outbreak on the army base where it had started. But that was not before a number of patients developed a neurological illness called Guillain-Barré syndrome as a result of taking the vaccine and 30 people died from complications that they would not otherwise have suffered. Despite the millions of lives saved by flu vaccines since—and the introduction of far stricter regulations governing the trial, approval, manufacture and distribution of vaccines—irrational fears about their safety persist across a broad swath of the American population.

自1976年人们对于猪流感的惶恐的开始，流感疫苗的危险性就开始在美国城市中流传。在流感最初爆发的陆军基地成功采取防控措施后，制药商大量赶制疫苗，四分之一的人口也匆匆接种疫苗以免这个计划取消。但此后不久便有一些接种疫苗的病人换上一种名为“格林-巴利综合症”的神经系统疾病，而另外有30人死于并发症，他们原本可能都不会感染的。尽管至今为止流感疫苗挽救了数百万人的性命，但是疫苗实验、审批、制造、配发这一系列的严格监管制度的介绍，在美国人中还是大量产生了为了寻求安全而引发的非理性恐惧。

Certainly, today’s added precautions have contributed to the delay in producing the new vaccine. So far, four vaccines against the H1N1 virus have been approved in the United States under the same process used by the Food and Drug Administration (FDA) for seasonal flu vaccines.

如今额外的预防措施使得新疫苗的投产延迟。到目前为止，4种对抗H1N1病毒的疫苗已经获得美国批准，其生产过程与美国食品药品监督管理局监管下的季节性流感疫苗生产过程相同。

Whether H1N1 or seasonal, influenza vaccines are made using hens’ eggs as factories. Millions of fertilised eggs are inoculated with small doses of flu virus and incubated to grow the large quantities of virus needed for a vaccination programme. When ready to be harvested, the tops of the eggs are sliced off and the virus collected. Sometimes it is killed to make it harmless, split to rid it of its fatty envelope and then purified to form the final dead vaccine. In other cases, the virus is merely crippled, so it cannot cause infection, and is then used as a nasal spray. Such attenuated live vaccines can be more effective, but are costlier to produce.

无论是H1N1型流感疫苗还是季节性流感疫苗的生产都是使用鸡胚。少剂量的流感病毒植入数百万受精卵中使其大量增殖用以供给生产疫苗所需的病毒。当病毒繁殖成功，将受精卵顶部开一个小口来收集病毒。有时病毒需要灭活使其无害。首先使病毒与其厚薄膜分离，然后进行纯化处理形成最终的灭活疫苗。其它的疫苗，病毒是做过减毒处理的，所以这种病毒不能导致感染，常用于鼻用喷剂。这种减毒活疫苗更有效但生产成本也很昂贵。

The trouble with using hens’ eggs for making killed or attenuated vaccines is that production cannot be ramped up quickly in an emergency. It takes months to get the hundreds of millions of eggs needed into production.

使用鸡胚生产灭活或是减毒活疫苗问题在于，即使是在紧急情况下也无法使产量迅速增加。要获得生产疫苗所需数千万的受精卵得花费几个月时间。

Earlier this year, the European Union approved a seasonal flu vaccine called Optaflu that is grown in large vats of living cells, instead of hen’s eggs—in much the same way as vaccines for chickenpox, polio and measles are made. The advantage of this approach is that it can be scaled up simply by adding more bioreactors to the plant. Novartis, which manufactures Optaflu, is currently building a plant in North Carolina, but has yet to get FDA approval for its cell-based vaccine.

今年年初，欧盟同意了一种名为Optaflu的季节性流感疫苗的投产。这种疫苗不是在鸡胚中培养的，而是在大的活细胞中培养，有些类似于水痘、骨髓灰质炎和麻疹疫苗的生产过程。这种生产方法的优点在于它可以通过增加植物的生物反应器来轻易地提高产量。Optaflu的生产商诺华制药目前正在北卡罗莱纳建厂，但是还需得到美国食品及药物管理局批准其生产细胞疫苗。

The technology has not stopped there. Instead of injecting proteins from a flu virus into a person’s body, why not inject just the micro-organism’s genes? Cells in a person’s body would then read those genes and start producing their own vaccine-like proteins. Engineering a vaccine this way would be even quicker than producing one from a cell culture.

生产技术并没有就此止步。相对向人体中注射从流感病毒中提取的蛋白质而言，为什么我们不直接注射微生物基因呢？人体细胞足以识别这些基因然后开始产生抗体。这样产生的疫苗比从细胞中产生要快的多。

Influenza’s genes are composed of RNA, not the more familiar DNA, but DNA is the more stable of the two molecules, so is preferred for making vaccines. (The genetic codes of RNA and DNA are slightly different, but are freely interchangeable.) Several years ago, researchers at the University of Pittsburgh made an artificial DNA vaccine for the H5N1 bird flu virus that was greatly feared at the time. To do so, they generated the DNA coding for the virus’s hemagglutinin gene(the H in a virus’s name)—which translates into a protein found on the surface of all influenza viruses. Finally, they spliced the hemagglutinin gene into a common-cold virus and used that to make a vaccine.

RNA（核糖核酸）是病毒中遗传信息的载体，与DNA（脱氧核糖核酸）不是十分相同，但是DNA是比较稳定的双分子螺旋结构，所以更易用于生产疫苗。（RNA与DNA的遗传密码有些轻微不同，但是可以自由转换。）几年前，当禽流感引起人们极大恐慌的时候，匹兹堡大学研究员研制出人工合成对抗H5N1型禽流感的DAN疫苗。为了研制这一疫苗，他们生产出病毒的红血球凝集素基因密码–这个基因转化成一种在所有流感病毒表面均存在的蛋白质。最后他们将红血球凝集素基因与普通流感病毒融合，并用其生产疫苗。

Injected into animals, the genetically engineered vaccine provided 100% protection against bird flu. The whole process—from receiving the genetic sequence by e-mail from the Centres for Disease Control and Prevention to testing the finished vaccine in animals—took roughly 30 days. Clinical trials using the technology are currently under way. Even so, it could be years before this sort of vaccine is deemed safe and effective enough for use in people.

在动物身上试验后发现，这种疫苗能100%的防治感染禽流感。从接收到疾病防控中心发来的基因序列的电邮到在动物身上实验已研制成的疫苗，这一过程大概只用了30天。临床实验中已经开始使用这种技术了。即使是这样，要确定这种疫苗在人体使用是安全有效的还是得需要几年时间。

Further off still is the ultimate goal: a universal flu vaccine that can be given just once in childhood and provides a lifetime’s protection against all forms of influenza. Your correspondent has no doubt that such a one-shot flu vaccine will one day be given to infants along with jabs against chickenpox. Alas, it is unlikely to happen in his own lifetime.

为长远打算才是我们最终的目标：只要在儿童时期接种一次全球性流感疫苗就可保护人们一生不受任何流感的侵袭。毫无疑问，这种一次接种即可的疫苗在未来的某天就会同水痘疫苗一样给婴儿接种。唉，只是在我们有生之年这可能不会实现了。