配套节目资料下载

下载常见问题解答

节目资料名称	下载位置
PDF 广播稿下载 (21 K)	中国电信·南京
MP3 声音下载 (915 K)	中国电信·南京
下载提示：请用右键点下载链接，在弹出菜单上选“目标另存为...”

---

This is the VOA Special English Science Report.

Researchers in the United States are beginning a study to see if a weaker version of an existing vaccine can protect people against the disease smallpox.

Smallpox is caused by the variola virus. It spreads from one person to another when an infected person coughs or sneezes. People who become infected show signs of the disease within two weeks. They develop high body temperature, head and back aches and large raised areas on the skin called sores. The disease can damage the brain and other body organs. Smallpox kills thirty percent of the people who get it. There is no treatment.

A vaccine medicine that prevents smallpox ended the threat of the disease around the world in Nineteen-Seventy-Seven. The virus was thought to exist only in the laboratories of two disease control centers in the world. One is in the United States. The other is in Russia.

Now, American officials fear that terrorists may have small amounts of the virus. The National Institute of Allergy and Infectious Diseases is supporting a study to see if a weakened smallpox vaccine can be effective against the disease.

Sharon Frey (FRI) is the leading researcher of the study. She says the United States has no more than twenty-million units of smallpox vaccine. That is not enough to protect two-hundred-eighty-five-million Americans from the virus. Scientists say making the vaccine weaker is a quick way to expand the amount of vaccine that already exists.

Doctor Frey and her team will test a weaker vaccine on more than six-hundred people at four medical centers in the United States.

One group of people will get the full-strength smallpox vaccine. The second group will get vaccine that is one-fifth as strong as the full-strength vaccine. The third group will get vaccine that is one-tenth as strong as the full-strength vaccine. The researchers will examine the people to see how many develop a reaction that means the vaccine is protecting them from smallpox. This reaction is a little raised area on the arm where the vaccine is given.

Doctor Frey expects to know the results in two to three months. She says that any use of the weakened vaccine will be a temporary measure until new supplies of the smallpox vaccine are ready. That will take about one to two years.

This VOA Special English Science Report was written by Nancy Steinbach.