This is the VOA Special English Development Report.

The World Health Organization has begun to use a new vaccine against polio. Officials say it will become a major tool in the campaign to end a disease that mainly affects children under age five. The new formulation is known as B.O.P.V., or bivalent oral polio vaccine.

It was used for the first time in December in a polio immunization campaign in Afghanistan.

Carol Pandak is with the PolioPlus program of the service organization Rotary International. She explains that health workers have been using what are called trivalent vaccines in some places. These are areas like Afghanistan where more than one kind of polio virus exists. There are three types of polio virus.

The trivalent vaccine is least effective against type three, more effective against type one and highly effective against type two. As a result, few new cases of type two have been reported since nineteen ninety-nine. This has led to greater use of monovalent vaccines to protect against either type one or type three polio.

But Carol Pandak says the monovalent vaccine is not enough in areas with both kinds of polio.

Rod Curtis at the World Health Organization in Geneva says the new bivalent vaccine solves this problem. Carol Pandak says tests found the new vaccine to be thirty percent more effective than the trivalent vaccine.

More than thirty new cases of polio were reported in Afghanistan last year. About half were type one and the others type three.

Rod Curtis says that shows the importance of the new vaccine targeting both viruses at once. Officials say similar vaccination campaigns are planned this year in India, Nigeria and Pakistan.

Intensive vaccination campaigns have reduced the number of new polio cases reported worldwide to fewer than two thousand a year.

The Global Polio Eradication Initiative says the number has fallen by ninety-nine percent since nineteen eighty-eight.

Polio is highly infectious. The virus enters the body through the mouth, usually in food or water. It grows in the intestines and attacks the nervous system.

One victim in two hundred suffers permanent paralysis, usually in the legs. Five to ten percent of those victims die when their breathing muscles fail.

And that's the VOA Special English Development Report. You can comment on our reports at our Web site, voaspecialenglish.com.