Hello there.  I can understand your concern.  Polio is caused by a virus.  Fracture by definition is a break in the continuity of the bone. The most common cause of which is trauma. Almost all people take injection at some point in their life, so if polio was to happen by injection, the whole world should have been affected by it. How do you even get such a doubt im wondering. Best regards. Dr. Anil kumar jain. Bangalore.