There clearly are risk factors for paralytic Polio disease but it's likely to be in the very complex interaction between the person's genome and the environment

There clearly are risk factors for paralytic Polio disease but it's likely to be in the very complex interaction between the person's genome and the environment, causing variability in certain types of immune responses. Even now it's not very clear how you would go about testing for them in advance. In the 1950s the "risk group" for a specific serotype of Polio virus is that you were statistically less likely to already have been infected with that serotype. They found out the Salk vaccine was almost entirely ineffective against transmissions pretty quick as well.