The World Health Organization currently plans to stop using oral polio vaccine three years after the detection of the last case of transmission of wild polio virus. This is because the vaccine contains live, weakened polio viruses that can spread and revert to virulence in populations that have not been immunized. Under this plan, an antiviral drug could be useful to control any polio outbreaks caused by vaccine derived virus that might occur after vaccination ends and the number of unimmunized people in the world steadily increases, the report says.
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