Vaccine May Have Spread Polio in US, Israel and Britain - VOA Learning English

The polio vaccine given by mouth is responsible for nearly wiping out the virus around the world. But, a number of recent cases in wealthy nations may be linked to the vaccine itself.

World health officials have nearly caused the dangerous polio virus to totally disappear by using a vaccine given by mouth rather than by injection. However, that same kind of vaccine is now linked … [+5211 chars]

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