https://en.wikipedia.org/wiki/Polio_vaccine#1987
An enhanced-potency IPV was licensed in the United States in November 1987, and is currently the vaccine of choice there.[19] The first dose of polio vaccine is given shortly after birth, usually between 1 and 2 months of age, and a second dose is given at 4 months of age.[19] The timing of the third dose depends on the vaccine formulation, but should be given between 6 and 18 months of age.[53] A booster vaccination is given at 4 to 6 years of age, for a total of four doses at or before school entry.[20] In some countries, a fifth vaccination is given during adolescence.[53] Routine vaccination of adults (18 years of age and older) in developed countries is neither necessary nor recommended because most adults are already immune and have a very small risk of exposure to wild poliovirus in their home countries.[19] In 2002, a pentavalent (five-component) combination vaccine (called Pediarix)[99][100] containing IPV was approved for use in the United States.[101][100]
Many thanks for the information.