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Malaria control efforts currently depend on things like chemically treated bed nets and spraying against mosquitoes. But scientists keep trying to find other ways to prevent the disease.

当前疟疾控制主要依赖于消毒蚊帐和喷药灭蚊等措施。但科学家一直在尝试寻找其它途径来预防疟疾。

A number of vaccines remain under development. Most contain genetically engineered versions of a few proteins from the Plasmodium parasite. Plasmodium is the organism that causes malaria. Those modified proteins are designed to get the body's defenses to launch an immune response against the Plasmodium. But the parasite contains thousands of proteins.

大量疫苗仍在研发阶段，其中多数包含疟原虫部分蛋白质的转基因版本。疟原虫是导致疟疾的生物体。这些改良过的蛋白质的作用是让人体免疫系统对疟原虫做出免疫反应。但这种寄生虫包含数千种蛋白质。

Another experimental vaccine includes a deactivated version of the entire parasite. Robert Seder is a researcher at the National Institute of Allergy and Infectious Diseases, near Washington.

另一种实验性疫苗包含整个寄生虫（蛋白质）的无活力版本。Robert Seder是华盛顿附近的美国过敏与传染病研究所的一名研究员。

ROBERT SEDER: "So instead of picking out one or two or three genes, you have the potential for what we call breadth -- generating an immune response that would be broad rather than narrower. And so that would be a good thing."

ROBERT SEDER：“所以我们不是挑选出两三种基因，而是拥有广度的潜能，能够产生广泛免疫反应。所以这将是一个好消息。”

Radiation is used to weaken the parasite so it cannot make people sick or get spread by a mosquito. To make the vaccine, scientists use the parasite at a time in its growth when the organism is called a sporozoite.

辐射被用于削弱寄生虫，使其不能致病或通过蚊虫传播。为了制造这种疫苗，科学家使用了在其生长过程中被称为孢子虫阶段的寄生虫。

This idea has been known since the nineteen sixties. But Mr. Seder says a discovery by a researcher at a vaccine company cleared the way for progress.

这个想法自上世纪60年代以来就被人熟知。但Seder先生表示，一位疫苗公司研究人员的发现为这一进程扫清了障碍。

ROBERT SEDER: "The major breakthrough here was that my collaborator, Stephen Hoffman at Sanaria, developed a method where he could isolate the sporozoites and purify them so that they could administer it as a vaccine to humans. And no one thought that was possible."

ROBERT SEDER：“这一重大突破是我的合作者，来自Sanaria公司的Stephen Hoffman研制出的一种新方法。在这种新方法中，他可以隔离孢子虫并将其净化，这样他们可以将其用于人类疫苗。此前没人认为这是可能的。”

But no one knew either if the weakened sporozoites would activate the immune system to protect against malaria. So researchers tested it on volunteers and found that it was safe. But it was not very effective. Only two out of forty-four volunteers were protected when bitten by malaria-infected mosquitoes.

但也没有人知道，这种弱化孢子虫是否会激活免疫系统以预防疟疾。因此，研究人员在志愿者身上进行了测试，并发现它是安全的，但不是非常有效。44名志愿者中，只有2人在被疟疾感染蚊虫叮咬时得到了预防。

To find out why, the researchers tested the vaccine on laboratory animals. They decided that the problem was the way the vaccine had been given to the volunteers. It was injected into the skin, to simulate the bite of a mosquito. Mr. Seder says it would have been more effective if it had been given directly into the blood.

为了找出原因，研究人员在实验室动物身上对疫苗进行了测试。他们认为问题出在给志愿者注射疫苗的方式上，疫苗是模拟蚊虫叮咬被注入皮肤。Seder先生表示，如果疫苗直接注入血液会更加有效。

However, vaccines are generally given by mouth or injected into the skin or muscle. Having to inject it into the blood could make vaccination programs more difficult if the vaccine is approved for general use.

然而，疫苗通常是口服或注射到皮肤或肌肉。如果疫苗被批准使用，注入血液会使疫苗接种程序更为困难。

For now, more testing is needed. A report on the study appeared in the journal Science.

现在需要进行更多测试。研究报告发表在《科学》杂志上。