Live-Virus Vaccine Testing
Testing the oral polio vaccine developed by Sabin posed challenges due to the already successful use of Salk’s vaccine in the United States. Despite this hurdle, Sabin managed to conduct successful field studies in the Soviet Union in 1957. The positive results from these trials led to the approval of Sabin’s vaccine for use in the United States in 1960. Subsequently, in 1961, Pfizer began mass-producing Sabin’s oral vaccine, which eventually replaced Salk’s injectable vaccine in many parts of the world.
Potential Concerns with the Live-Virus Vaccine
Controversy surrounded the choice between two polio vaccines. While there were indications that the live vaccine had the potential to trigger paralytic polio in rare instances, Sabin, the developer of the live vaccine, dismissed these claims. On the other hand, Salk, the creator of the killed-virus vaccine, firmly believed that his vaccine was equally effective without any associated risks of paralysis. Consequently, in 1999, the United States reverted to exclusively using Salk’s killed-virus vaccine due to the minimal possibility of the live oral vaccine causing polio.