1962

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 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. Vaccine-derived polio cases happen in places where vaccination rates are low. According to the Global Polio Eradication Initiative, there were 959 cases of vaccine-derived polio worldwide in the year 2020. The oral polio vaccine (OPV) still has many benefits: the live attenuated (weakened) vaccine virus provides better immunity in the gut, which is where polio replicates. But the vaccine virus is also excreted in the stool, and in communities with low-quality sanitation and low immunization rates, this means that it can be spread from one unvaccinated child to another over a long period of time (often over the course of about 12-18 months) where it can mutate and take on a form that can cause paralysis just like the wild poliovirus. Vaccination is the key to eradication.