设想与效益

Science & Technology
AIDS 艾滋病
　
The ideal and the good
设想与效益
　
Nov 27th 2008
From The Economist print edition

Deploying the drugs used to treat AIDS may be the way to limit its spread
　　
　　有效地利用治疗艾滋病的药物也许是限制其蔓延的方法
　　
Illustration by Peter Schrank
 
　　
IT HAS become a cliché among doctors who deal with AIDS that the only way to stop the epidemic is to develop a vaccine against HIV, the virus that causes it. Unfortunately, there is no sign of such a thing becoming available soon. The best hope was withdrawn from trials just over a year ago amid fears that it might actually be making things worse. As a result, vaccine researchers have mostly gone back to the drawing board of basic research. Meanwhile, the virus marches on. Last year, according to UNAIDS, the international body charged with combating it, 2.7m people were infected, bringing the estimated total to 33m.
　
　　抑制艾滋病的唯一方法是开发抗艾滋病病毒的疫苗，这种说法在研究艾滋病的医生中已经是一种老生常谈了。不幸的是，还没有迹象表明有效的疫苗会很快出现。最大希望寄托于一年前进行的一些实验，人们在担心着艾滋病的蔓延可能会变得更加严重，因此疫苗研究人员主要从重新进行基础研究开始。与此同时，艾滋病病毒在继续扩散。按照联合国艾滋病联合工作组（担负着抗艾滋病任务的国际机构）的统计，去年有二百七十万人被感染，这将估计的患者总人数提高到三千三百万。
　　
Reuben Granich and his colleagues at the World Health Organisation (WHO), though, have been exploring an alternative approach. Instead of a vaccine, they wonder, as they write in the Lancet, whether the job might be done with drugs.
　　
　　然而，鲁本•格然尼克和其在世界卫生组织的同事在探索一种替代性方法。正如他们在《柳叶刀》的论文中所写，他们想知道，作为对疫苗方法的替代，是否可以使用药物进行。
　　
In the spread of any contagious disease, each act of infection has two parties, one who already has the disease and one who does not. Vaccination works by treating the uninfected individual prophylactically. Since it is impossible to say in advance who might be exposed, that means vaccinating everybody. The alternative, as Dr Granich observes, is to treat the infected individual and thus stop him being infectious. For this to curb an epidemic would require an enormous public-health campaign of the sort used to promote vaccination. But that campaign would be of a different kind. It would have to identify all (or, at least, almost all) of those infected. It would then have to persuade them to undergo not a short, simple vaccination course, but rather a drug regime that would continue indefinitely.
　　
　　在任何接触性传染病的传播中，每一次传染都涉及两类人，一类是已患病者，一类是未患病者。接种疫苗是通过预防性地治疗未感染者而起作用。因为事先知道谁可能被感染是不可能的，这就意味着要给每个人接种疫苗。格然尼克说，这种替代性方法是治疗已患病者，因而使其丧失感染性。为了达到抑制某一传染病，需要进行一种大规模的公共健康运动以促进接种疫苗。然而与替代性方法不同，这种运动必需鉴定所有或大部分的未感染者，然后说服他们接受一个时间并不短而且不是很简单的接种疫苗过程，或者说是一个不能确定持续多久的药物疗程。
　　
Pills, not needles
使用药剂而非针剂
　　
The first question to ask of such an approach is, could it work in principle? It is this that Dr Granich and his colleagues have tried to answer. Using data from several African countries, they have constructed a computer model to test the idea. In their ideal world, everyone over the age of 15 would volunteer for testing once a year. If found to be infected, they would be put immediately onto a course of what are known as first-line antiretroviral drugs (ARVs). These are reasonably cheap, often generic, pharmaceuticals that, although they do not cure someone, do lower the level of the virus in his body to the extent that he suffers no symptoms. They also—and this is the point of the study—reduce the level enough to make him unlikely to pass the virus on. For the 3% or so of people per year for whom the first-line ARVs do not work, more expensive second-line treatments would be used.
　　
　　对于这样的替代性方法，第一个疑问是从原则上说来其是否有效？这正是格然尼克医生和其同事所要回答的。他们使用来自一些非洲国家的数据建立了一个计算机模型，以检验这一设想。按他们设想的理想状况，每个年龄超过十五岁的人将自愿每年参加一次检验。如果发现被感染，他们将立即被进行一个称为首期抗逆转录病毒药物治疗的过程（ARVs），这些药物是相当廉价、经常使用的普通药物，虽然它们不能治愈每个患者，但能够降低患者体内病毒的数量，达到使其不出现症状的程度。这些药物也将病毒数量降低到足以使其不可能再继续传播病毒（这正是研究的要点）。每年有大约3%的人，首期ARVs治疗不起作用，因此较昂贵的二期治疗将被使用。

When Dr Granich crunched the numbers through the model, he concluded that if this scheme could be implemented, it would do the trick. The rate of new infections (now 20 per 1,000 people per year) would fall within ten years of full implementation to one per 1,000 per year. Within 50 years the prevalence of HIV would drop below 1%, compared with up to 30% at the moment in the worst-affected areas.
　　
　　当格然尼克医生通过计算机模型处理了这些数据时，他得出结论，如果这一方案被实施，将会成功。新的感染率将在方案完全实施的十年内，降低到每年1‰（现在是每年20‰）。五十年内，艾滋病的患病率将下降到低于1%，目前在最严重的感染地区达30%。
　　
Whether such an approach could be made to work in practice—and if it could, whether it should—are two other questions. The existing plan for combating HIV centres on saving the lives of those already infected. The intention is to make ARVs available to everyone who needs them, in rich and poor countries alike, by buying the drugs cheaply and building the infrastructure of doctors, nurses and clinics to prescribe and provide them. “Needs”, however, is defined as “at risk of developing symptoms”. People with HIV often remain asymptomatic for years, and conventional wisdom is that treating such people brings little clinical benefit while exposing them to unpleasant side effects such as nausea, vomiting and diarrhoea.
　　
　　是否这种方法在实际运用中会起作用，如果它有这种可能，是否将会发挥出来，这是另外两个疑问。现存的抗艾滋病病毒的方法是以挽救已感染患者的生命为中心。这种方法的目的是通过购买廉价的药物，建立处方并提供这些药物的医生、护士和门诊部的基本制度，实行可用于每个需要的患者的ARVs治疗，在富裕和贫穷的国家都是这样。然而，“需要”被定义为“处于症状发展的危险中”。携带有艾滋病病毒的病人经常维持无症状达数年，传统观点认为，治疗这样的病人几乎没有临床益处，同时使它们易于遭受不愉快的副作用，象恶心、呕吐和腹泻。
　　
Even vaccination bothers some medical ethicists because, although it does protect the vaccinated individual, governments promote it in order to create “herd immunity”—from which the unvaccinated will also benefit. Treating asymptomatic carriers of HIV causes greater qualms if it brings no benefit to the people actually taking the medicine. However, Kevin De Cock, one of Dr Granich’s colleagues, points out that the latest research suggests such people are not as asymptomatic as had once been thought. They may suffer from illnesses such as heart, kidney and liver diseases and cancers that are not classical symptoms of AIDS. Indeed, a recent study suggested that deferring treatment until classical symptoms appear increases the chance of someone dying by 70%.
　　
　　接种疫苗甚至也使某些医学伦理学家感到烦恼，因为，这虽然保护了接种疫苗的患者，但政府提倡它是为了获得“群体免疫”——使未接种疫苗者也从中受益。如果治疗已接受这种药物的无症状的艾滋病病毒携带者没有产生效益，会导致更大的疑虑。然而，格然尼克医生的同事凯文•德•考克指出，最近的研究认为，这些患者不是象以往认为的那样无症状，他们可能患有象心脏病、肾病、肝病和癌症这样的疾病，但不是典型的艾滋病症状。实际上，最近的研究表明，推迟治疗直到典型的症状出现，将使患者的死亡几率增加到70%。
　　
If that result is confirmed, it would change the ethics completely. It would also make it easier to persuade people to come in once a year for testing at their local clinic, even if they felt well. And it would create pressure for the current policy to be reviewed anyway, so that something like the scheme Dr Granich and his colleagues have been investigating might end up happening by default.
　　
　　如果这个结果被证实，它将完全改变人们的行为准则。即使是感觉良好的人，说服他们去当地的诊所每年进行一次体检将变得容易。而且它无论如何会对重新审视当前的政策产生压力，因此象格然尼克医生和其同事们一直在研究的方法可能会消除因疏忽导致的意外情况。
　　
If the scheme were implemented (and the WHO is at pains to point out that this paper in no way indicates a change of policy), it would be more costly to begin with than the existing plan of universal access. However, that would change over the years, as the caseload fell. This seems, therefore, to be an approach worth exploring. AIDS doctors are not so spoilt for options that they can afford to ignore new ones. Employing the logic of vaccination using proven drugs may be an idea whose time has come.
　　
　　如果这个方法被实施（世界卫生组织尽力指明，这个论文绝不意味着政策的改变），首先它将比现在普遍使用的方法更昂贵，然而，经过一些年当发病量下降时，这一情况将改变。因此，这似乎是一个值得探索的方法。艾滋病医生们并没有被可选择性的方法所干扰，以至于他们可以忽视这些新的方法。使用被证实的药物进行接种疫苗这一逻辑也许是一个早就确立的思路。