VOA慢速英语2020 多少人接种疫苗才能形成群体免疫？

Governments and officials around the world are hoping COVID-19 vaccines² can create "herd³ immunity⁴" to protect large populations.

世界各地的政府和官员都希望新冠疫苗能够产生“群体免疫”，以保护大量人口。

Some experts predict that giving a vaccine¹ to just two-thirds of a population could protect whole communities or nations. But the effectiveness of such efforts is highly dependent on what the vaccines will be able to prevent.

有专家预测，仅需要2/3的人口接种疫苗就能保护整个社区或国家。但是这种措施的有效性很大程度上取决于疫苗能够预防什么。

What is herd immunity?

什么是群体免疫？

Herd immunity happens when a large percentage "of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune," the Mayo Clinic notes on its website.

梅奥诊所在其网站上表示，当社区中很大一部分人口对某种疾病免疫，使得这种疾病无法在人与人之间传播，这就形成了群体免疫。于是整个社区得到了保护，而不仅仅是获得免疫的人。

But there are still many open questions about herd immunity and COVID-19 vaccines.

但是关于群体免疫和新冠疫苗仍存在许多悬而未决的问题。

For example, will the first vaccines be able to stop the spread of the virus, or just stop people from getting sick? How many people in a population will accept a vaccine? Will vaccines offer the same protection to everyone?

例如，第一批疫苗是否能够阻止这种病毒的传播？还是只能阻止人们患病？有多少人会接种疫苗？疫苗是否会给每个人提供相同的保护？

Josep Jansa is an expert at the Stockholm-based European Centre for Disease Prevention and Control (ECDC).

何塞普·扬绍是位于斯德哥尔摩的欧洲疾病预防和控制中心的专家。

"Herd immunity is sometimes wrongly understood as individual protection," Jansa told the Reuters news agency. He added, "Herd immunity refers to community protection, not to how an individual is protected."

扬绍对路透社表示：“群体免疫有时候被错误理解为个体防护。”他还表示：“群体免疫是指社区防护，而不是指个体如何得到防护。”

R Value and disease spread

R值和疾病传播

One of the central questions about herd immunity and COVID-19 is the reproduction rate, or R value, of the virus that causes it. R value is a measure of how many people get the virus from an average infected individual in environments where no restrictions⁵ are in place. For example, an R value of 2 means an infected person would be expected to pass the virus on to 2 other people.

有关群体免疫和新冠肺炎的核心问题之一是这种病毒导致的传染指数或R值。R值是用于衡量在没有任何限制的环境中，有多少人会从普通患者身上感染病毒。例如，R值为2就意味着一名感染者会传染另外两个人。

Winfried Pickl is a professor at the Medical University of Vienna.

Winfried Pickl是维也纳医科大学教授。

"The problem is that for now we don't know exactly how fast the virus spreads without any precautions and with the normal travel and social activities we had a year ago," Pickl told Reuters.

Pickl对路透社表示：“问题是，目前我们不知道该病毒在没有任何预防措施的情况下，它在我们一年前这种正常的旅行和社交活动中的传播速度。”

Health experts have noted⁶ that anything less than 100 percent vaccine efficacy would require an increase in vaccinations⁸ to reach herd immunity. Early data on the leading COVID-19 vaccines – from Pfizer-BioNTech and Moderna - suggests only about 90 percent efficacy.

卫生专家指出，若疫苗效果低于100%，则需要增加疫苗接种量才能达到群体免疫。辉瑞公司联合BioNTech公司以及莫德纳公司提供的主要新冠疫苗的早期数据表明，其有效率仅为90%左右。

Amesh Adalja is with the Johns Hopkins Center for Health Security. He said a good target for immunity in the United States would be to have more than 70 percent of the population vaccinated⁹. But the number could go up if vaccines are less effective, he added.

Amesh Adalja任职于约翰霍普金斯大学健康安全中心。他说，美国实现群体免疫的目标是让70%以上的人口接种疫苗。但他还说，如果疫苗效果不好，这一数字可能还会上升。

The ECDC uses an estimated herd immunity level of 67 percent for its models. In Germany, Chancellor¹⁰ Angela Merkel said this month that COVID-19 restrictions there could be lifted once 60 to 70 percent of the population reached immunity.

欧洲疾病预防和控制中心在其模型中采用了67%的群体免疫率。德国总理安哥拉·默克尔本月表示，一旦有60%到70%的人口获得免疫，就可以取消新冠肺炎限制措施。

World Health Organization experts have also suggested a 65 to 70 percent vaccine coverage¹¹ rate as a way to reach population immunity through vaccination⁷.

世卫组织专家还建议疫苗覆盖率达到65%到70%，以此作为通过疫苗接种获得群体免疫的途径。

Vaccines and virus transmission

疫苗和病毒传播

Experts say another important question is whether vaccines can stop the spread of the coronavirus, which causes the disease COVID-19.

专家表示，另一个重要问题是这些疫苗是否能阻止导致新冠肺炎的新冠病毒传播。

Evidence so far suggests the first COVID-19 vaccines will at least stop people from developing the disease. But it cannot be ruled out that people will still catch the virus and pass it on to others.

迄今为止的证据表明，首批新冠疫苗将至少能阻止人们患病。但是不能排除人们仍然会感染并病毒并传播给他人。

Bodo Plachter is a professor and deputy director of the Institute of Virology at Germany's Mainz University teaching hospital. Plachter said that respiratory infections can be hard to block completely with vaccines - although the shots are expected to reduce the amount of virus that is moving around.

博多·普拉希特是德国美因茨大学教学医院病毒研究所的教授兼副所长。普拉希特表示，用疫苗很难完全阻断呼吸道感染，尽管注射疫苗可以减少正在传播的病毒数量。

"It may well be that vaccinated people will shed fewer viruses," he said. "But it would be a mistake," he added, to think that "vaccination alone can suppress a pandemic."

他说：“接种疫苗者很可能会降低病毒的传播。”他还表示：“但是认为仅仅接种疫苗就能抑制大流行的观点是错误的。”

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 herd   

n.兽群，牧群；vt.使集中，把…赶在一起

参考例句：

• She drove the herd of cattle through the wilderness.她赶着牛群穿过荒野。
• He had no opinions of his own but simply follow the herd.他从无主见，只是人云亦云。

4 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。

5 restrictions   

约束( restriction的名词复数 )； 管制； 制约因素； 带限制性的条件（或规则）

参考例句：

• I found the restrictions irksome. 我对那些限制感到很烦。
• a snaggle of restrictions 杂乱无章的种种限制

6 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

7 vaccination   

n.接种疫苗，种痘

参考例句：

• Vaccination is a preventive against smallpox.种痘是预防天花的方法。
• Doctors suggest getting a tetanus vaccination every ten years.医生建议每十年注射一次破伤风疫苗。

8 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》

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 chancellor   

n.(英)大臣；法官；(德、奥)总理；大学校长

参考例句：

• They submitted their reports to the Chancellor yesterday.他们昨天向财政大臣递交了报告。
• He was regarded as the most successful Chancellor of modern times.他被认为是现代最成功的财政大臣。

11 coverage   

n.报导，保险范围，保险额，范围，覆盖

参考例句：

• There's little coverage of foreign news in the newspaper.报纸上几乎没有国外新闻报道。
• This is an insurance policy with extensive coverage.这是一项承保范围广泛的保险。