Since the year 2000, the Sabin vaccine (also called the oral polio vaccine or OPV) has been discontinued in the United States, although it is still being used in other countries.
It contains the live, but weakened, poliovirus and because OPV uses the live virus, it has the potential to cause infection in individuals with weak immune defenses (both in the person who receives the vaccine and in close contacts).
Approximately nine cases a year of vaccine related polio was associated with OPV in the United States.