USA HISTORY

Detailed explanation-1: -Two polio vaccines, the inactivated polio vaccine (IPV) and the live-attenuated oral polio vaccine (OPV) became available in 1955 and 1963, respectively (Plotkin, 2014), both able to protect against all three wild types of polio virus.

Detailed explanation-2: -By the mid-20th century, the poliovirus could be found all over the world and killed or paralysed over half a million people every year. With no cure, and epidemics on the rise, there was an urgent need for a vaccine.

Detailed explanation-3: -The basis for vaccination began in 1796 when the English doctor Edward Jenner noticed that milkmaids who had gotten cowpox were protected from smallpox.

Detailed explanation-4: -The first inactivated polio vaccine (IPV) was produced by Salk using virus grown on monkey kidney cells and inactivated with formalin. In 1954, the inactivated vaccine was tested in a placebo-controlled trial, which enrolled 1.6 million children in Canada, Finland and the United States[13].

Detailed explanation-5: -1955. The polio vaccine developed by Dr. Salk and colleagues is licensed in the U.S. Before the polio vaccine, the disease had been a major cause of disability in children. About 16, 000 cases of polio (paralytic poliomyelitis) occurred each year in the U.S. in the 20th century compared with none in 2020.