VOA慢速英语2020--旧疫苗对预防COVID-19有效吗？

Do Old Vaccines² Help Protect Against COVID-19?

Scientists want to find out if vaccines already in existence might provide protection against COVID-19.

The idea does not seem to make sense. Vaccines are designed to target a single virus or bacterium³. But vaccines made using active strains of bacteria or viruses seem to help the body's natural defenses, called the immune system, fight non-targeted diseases as well.

There is no evidence yet that such vaccines could improve the immune system enough to resist the new coronavirus. But, a COVID-19 vaccine¹ is expected to take 12 to 18 months. So, some researchers say it is time to test a tuberculosis⁵ vaccine for possible effects on the new coronavirus.

Dr. Mihai Netea is with Radboud University Medical Center in the Netherlands. He says if the TB vaccine works, "it could be a very important tool to bridge this dangerous period" until a COVID-19 vaccine is available.

The World Health Organization on Monday strongly warned against the use of the tuberculosis vaccine against COVID-19 until studies prove it works. Netea's team is leading such a study already involving almost 1,500 Dutch health care workers as subjects. The researchers are treating some of the workers with the TB vaccine called BCG. It is made of a live but weakened bacterium related to TB bacteria. The other study subjects are treated with a placebo⁶, an inactive substance.

Another study of BCG is taking place with 4,000 hospital workers in Australia. Similar research is being planned in other countries, including the United States.

Another possibility for treatment is a polio vaccine made of live but weakened polio viruses. The Global Virus Network in Baltimore, Maryland wants to begin studies with that vaccine, which is taken by mouth. Dr. Robert Gallo, a founder⁷ of the group, told The Associated Press that he is discussing the idea with health officials.

Jennifer Routh of the U.S. National Institutes of Health also said researchers there are discussing TB and polio vaccines as a possible COVID-19 defense⁴.

Live vaccines, however, are risky⁸ for people with weakened immune systems. They should not be tried against COVID-19 outside of a research study, said Dr. Denise Faustman. She is immunobiology chief at Massachusetts General Hospital and is planning a TB vaccine study.

She added that her study provides a good chance "to prove or disprove this off-target effect."

Early evidence

Years ago, scientists began noticing that people vaccinated⁹ with some live vaccines had improved immunity¹⁰ to non-targeted sicknesses.

The TB vaccine, for example, is given mostly to babies in developing countries. It offers only partial protection against bacterial¹¹ TB. But studies suggested that the vaccinated babies had better survival rates and resisted lung infections better.

In 2018, Netea's team published a more direct test. It showed that BCG vaccine increases immunity overall. In fact, it was good enough to at least partly block another virus given experimentally a month later.

There has been a report that researchers in the former Soviet¹² Union found that influenza¹³ cases dropped after polio vaccinations¹⁴ in the 1970s.

And in 2015, Danish researchers found similar results with polio vaccinations given by liquid drops through the mouth. These are still used in developing countries, while the U.S. and other areas use the inactivated¹⁵ shot for childhood vaccines.

Immunity from live vaccines

The goal of a vaccine is to prepare the body to recognize a targeted health threat. Vaccines cause the body to make antibodies, products in the blood that fight bacteria and viruses. BCG appears to influence immune cells so they can more readily remove germs in general, said Netea, the Dutch researcher.

Scientists not involved in the effort to try these vaccines against COVID-19 told the AP that such studies are worthwhile.

Words in This Story

strain –n. a group of closely related living things

1 vaccine   

n.牛痘苗，疫苗；adj.牛痘的，疫苗的

参考例句：

• The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
• She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。

2 vaccines   

疫苗，痘苗( vaccine的名词复数 )

参考例句：

• His team are at the forefront of scientific research into vaccines. 他的小组处于疫苗科研的最前沿。
• The vaccines were kept cool in refrigerators. 疫苗放在冰箱中冷藏。

3 bacterium   

n.(pl.)bacteria 细菌

参考例句：

• The bacterium possibly goes in the human body by the mouth.细菌可能通过口进入人体。
• A bacterium is identified as the cause for his duodenal ulcer.一种细菌被断定为造成他十二指肠溃疡的根源。

4 defense   

n.防御，保卫；[pl.]防务工事；辩护，答辩

参考例句：

• The accused has the right to defense.被告人有权获得辩护。
• The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。

5 tuberculosis   

n.结核病，肺结核

参考例句：

• People used to go to special health spring to recover from tuberculosis.人们常去温泉疗养胜地治疗肺结核。
• Tuberculosis is a curable disease.肺结核是一种可治愈的病。

6 placebo   

n.安慰剂；宽慰话

参考例句：

• The placebo has been found to work with a lot of different cases.人们已发现安慰剂能在很多不同的病例中发挥作用。
• The placebo effect refers to all the observable behaviors caused by placebo.安慰剂效应是指由安慰剂所引起的可观察的行为。

7 Founder   

n.创始者，缔造者

参考例句：

• He was extolled as the founder of their Florentine school.他被称颂为佛罗伦萨画派的鼻祖。
• According to the old tradition,Romulus was the founder of Rome.按照古老的传说，罗穆卢斯是古罗马的建国者。

8 risky   

adj.有风险的，冒险的

参考例句：

• It may be risky but we will chance it anyhow.这可能有危险，但我们无论如何要冒一冒险。
• He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。

9 vaccinated   

[医]已接种的，种痘的，接种过疫菌的

参考例句：

• I was vaccinated against tetanus. 我接种了破伤风疫苗。
• Were you vaccinated against smallpox as a child? 你小时候打过天花疫苗吗？

10 immunity   

n.优惠；免除；豁免，豁免权

参考例句：

• The law gives public schools immunity from taxation.法律免除公立学校的纳税义务。
• He claims diplomatic immunity to avoid being arrested.他要求外交豁免以便避免被捕。

11 bacterial   

a.细菌的

参考例句：

• Bacterial reproduction is accelerated in weightless space. 在失重的空间，细菌繁殖加快了。
• Brain lesions can be caused by bacterial infections. 大脑损伤可能由细菌感染引起。

12 Soviet   

adj.苏联的，苏维埃的；n.苏维埃

参考例句：

• Zhukov was a marshal of the former Soviet Union.朱可夫是前苏联的一位元帅。
• Germany began to attack the Soviet Union in 1941.德国在1941年开始进攻苏联。

13 influenza   

n.流行性感冒，流感

参考例句：

• They took steps to prevent the spread of influenza.他们采取措施
• Influenza is an infectious disease.流感是一种传染病。

14 vaccinations   

n.种痘，接种( vaccination的名词复数 )；牛痘疤

参考例句：

• Vaccinations ensure one against diseases. 接种疫苗可以预防疾病。 来自《简明英汉词典》
• I read some publicity about vaccinations while waiting my turn at the doctor's. 在医生那儿候诊时，我读了一些关于接种疫苗的宣传。 来自《简明英汉词典》

15 inactivated   

v.使不活泼，阻止活动( inactivate的过去式和过去分词 )

参考例句：

• Molluscicides are quickly inactivated by sunlight and adsorption to mud organic matter. 灭螺剂因阳光作用、泥土及有机物质的吸收会很快失效。 来自辞典例句
• Viruses were inactivated by BPL and the toxicity measured again. BPL对病毒进行灭活，测定残存毒力。 来自互联网