Measles(麻疹), which once killed 450 children each year and disabled even more, was nearly wiped out in the United States 14 years ago by the universal use of the MMR vaccine(疫苗). But the disease is making a comeback, caused by a growing anti-vaccine movement and misinformation that is spreading quickly. Already this year,115 measles cases have been reported in the USA, compared with 189 for all of last year.
麻疹曾经每年导致450名儿童死亡，并且使更多的人残疾，但14年前在美国几乎被普遍使用的MMR疫苗所根除。但是，由于日益增长的反疫苗运动和迅速传播的错误信息，这种疾病正在卷土重来。今年已经有115例麻疹病例报告，而去年全年只有189例。

The numbers might sound small, but they are the leading edge of a dangerous trend. When vaccination rates are very high, as they still are in the nation as a whole, everyone is protected. This is called“herd immunity”, which protects the people who get hurt easily, including those who can’t be vaccinated for medical reasons, babies too young to get vaccinated and people on whom the vaccine doesn’t work.
这些数字可能听起来不多，但它们是一个危险趋势的先兆。当疫苗接种率非常高时，就像整个国家仍然那样，每个人都受到保护。这被称为“群体免疫”，它保护那些容易受伤的人，包括因医疗原因无法接种疫苗的人、太小而无法接种疫苗的婴儿以及疫苗不起作用的人。

But herd immunity works only when nearly the whole her d joins in. When some refuse vaccination and seek a free ride, immunity breaks down and everyone is in even bigger danger.
但是，只有当几乎所有群体成员都参与时，群体免疫才能起作用。当一些人拒绝接种疫苗并寻求免费搭车时，免疫就会瓦解，每个人都面临更大的危险。

That’s exactly what is happening in small neighborhoods around the country from Orange County, California, where 22 measles cases were reported this month, to Brooklyn,N. Y., where a 17-year-old caused an outbreak last year.
这正是在全国各地的小社区中发生的事情，从本月报告了22例麻疹病例的加利福尼亚州橙县，到去年一个17岁的年轻人引发疫情的纽约布鲁克林。

The resistance to vaccine has continued for decades, and it is driven by a real but very small risk. Those who refuse to take that risk selfishly make others suffer.
对疫苗的抵制已经持续了几十年，这是由一个真实但非常小的风险驱动的。那些拒绝承担这种风险的人自私地使他人受苦。

Making things worse are state laws that make it too easy to opt out(决定不参加) of what are supposed to be required vaccines for all children entering kindergarten. Seventeen states allow parents to get an exemption(豁免), sometimes just by signing a paper saying they personally object to a vaccine.
使情况更糟的是，一些州的法律使得选择退出本应是所有进入幼儿园的儿童必须接种的疫苗变得太容易。有17个州允许父母获得豁免，有时只需签署一份声明他们个人反对疫苗的文件。

Now, several states are moving to tighten laws by adding new regulations for opting out. But no one does enough to limit exemptions.
现在，几个州正在通过增加新的退出规定来收紧法律。但是没有人做得足够来限制豁免。

Parents ought to be able to opt out only for limited medical or religious reasons. But personal opinions? Not good enough. Everyone enjoy s the life -saving benefits vaccines provide, but they’ll exist only as long as everyone shares in the risks.
父母应该只能基于有限的医疗或宗教原因选择退出。但是个人意见呢？这还不够好。每个人都享受着疫苗提供的救命好处，但只有当每个人都共同承担风险时，这些好处才会存在。

1. The first two paragraphs suggest that _.
   A. a small number of measles cases can start a dangerous trend
   B. the outbreak of measles attracts the public attention
   C. anti-vaccine movement has its medical reasons
   D. information about measles spreads quickly
   答案：A

2. Herd immunity works well when _.
   A. exemptions are allowed
   B. several vaccines are used together
   C. the whole neighborhood is involved in
   D. new regulations are added to the state laws
   答案：C

3. What is the main reason for the comeback of measles?
   A. The overuse of vaccine.
   B. The lack of medical care.
   C. The features of measles itself.
   D. The vaccine opt-outs of some people.
   答案：D

4. What is the purpose of the passage?
   A. To introduce the idea of exemption.
   B. To discuss methods to cure measles.
   C. To stress the importance of vaccination.
   D. To appeal for equal rights in medical treatment.
   答案：C