Vaccine May Have Spread Polio in US, Israel and Britain

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.

Source : https://learningenglish.voanews.com/a/vaccine-may-have-spread-polio-in-us-israel-and-britain/6711987.html