Sabin vaccine replaced Salk as the most used polio vaccine
By 1962, the Sabin oral polio vaccine (OPV) replaced the Salk inactivated polio vaccine (IPV) as the most used polio vaccine. The Sabin OPV provided longer lasting immunity than the Salk vaccine. This resulted in a clash between the two rival camps, but the Sabin vaccine won out in 1962.
However, since Since 2000, only IPV has been used in the United States, to completely eliminate the risk of vaccine-derived polio that can occur with OPV (since it is a live, attenuated virus vaccine). However, OPV is still used in many places throughout the world today.
