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 greate

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